GIFT  OF 
Dean  Frank  H.  Probert 


Mining  Dept. 


WORKS  OF 
PROF.   WALTER   R.   CRANE 

PUBLISHED   BY 

JOHN  WILEY  &  SONS  INC. 


Gold  and  Silver 

Comprising  an  Economic  History  of  Mining  in 
the  United  States,  the  Geographical  and  Geo- 
logical Occurrence  of  the  Precious  Metals,  with 
their  Mineralogical  Associations,  History  and 
Description  of  Methods  of  Mining  and  Extrac- 
tion of  Values,  and  a  Detailed  Discussion  of  the 
Production  of  Gold  and  Silver  in  the  World  and 
the  United  States,  x  +  727  pages,  G  by  9,  illus- 
trated. Cloth,  $5.00  net. 

Index  of  Mining  Engineering  Literature 

Comprising  an  Index  of  Mining,  Metallurgical, 
Civil,  Mechanical,  Electrical,  and  Chemical  En- 
gineering Subjects  as  Related  to  Mining  Engineer- 
ing. Vol.  I,  xii  +  812  pages,  6  by  9.  Cloth,  $4.00 
net.  Morocco,  $5.00  net. 

Vol.  II,  xiii  +  445  pages,  6  by  9.  Cloth,  $3.00  net. 
Morocco,  $4.00  net. 

Ore  Mining  Methods 

Comprising  descriptions  of  methods  of  support  in 
extraction  of  ore,  detailed  descriptions  of  methods 
of  stoping  and  mining  in  narrow  and  wide  veins 
and  bedded  and  massive  deposits,  including  stull 
and  square -set  mining,  filling  and  caving  methods, 
open-cut  work  and  a  discussion  of  costs  of  Mining. 
ix  +  277  pages,  6  by  9.  35  full-page  plates  and 
48  illustrations  in  text.  Cloth,  $3.50  net. 


ORE  MINING  METHODS 

COMPRISING 

DESCRIPTIONS  OF  METHODS   OF  SUPPORT  IN  EXTRACTION 
OF  ORE,  DETAILED  DESCRIPTIONS  OF  METHODS  OF  DE- 
VELOPMENT OF  MINES,  OF  STOPING  AND  MINING  IN 
NARROW   AND  WIDE  VEINS   AND  BEDDED  AND 
MASSIVE  DEPOSITS  INCLUDING  STULL  AND 
SQUARE-SET     MINING,     FILLING     AND 
CAVING    METHODS,    OPEN    CUT 
WORK   AND    A    DISCUSSION 
OF   COSTS    OF   MINING 


BY 

WALTER    R.    CRANE,    PH.D. 

K  ' 

DEAN   OF   THE    SCHOOL   OF    MINES,   AND    PROFESSOR    OF    MINING, 
THE    PENNSYLVANIA   STATE    COLLEGE 


SECOND    EDITION 


NEW  YORK 

JOHN    WILEY    &    SONS,   INC. 

LONDON:   CHAPMAN   &   HALL,   LIMITED 

1917 


GIFT  OF 

WAN  FRANK  H  PROSE«I 


COPYRIGHT,  IQI;, 

BY 
WALTER   R.    CRANE 


Stanbopc 

F.    H.GILSON   COMPANY 
BOSTON,  U.S.A. 


PREFACE 

WHILE  much  has  been  written  with  regard  to  methods 
of  mining  ore  and  many  excellent  descriptions  of  the 
methods  employed  in  the  mines  of  the  United  States  and 
abroad  are  to  be  found  in  the  technical  press,  yet  there  is 
no  work  in  which  systematic  and  detailed  descriptions  of 
the  various  typical  methods  are  to  be  found. 

The  writer  has  therefore  attempted  to  prepare  a  work 
on  ore  mining  methods  alone,  which  it  is  hoped  may  prove 
useful  to  both  the  student  and  the  practical  man  in  acquir- 
ing a  knowledge  of  ore  mining  and  in  comparing  methods. 
That  the  work  may  be  of  the  most  service,  the  descrip- 
tions have  been  made  brief  and  many  illustrations  em- 
ployed to  supplement  them.  Illustrations  taken  from 
photographs  of  mine  models  have  been  extensively  used 
and  possess  the  advantage  over  diagrams  in  that  by  relief 
three  dimensions  are  shown.  Further,  the  application  of 
each  method  has  been  specifically  stated,  together  with 
the  advantages  and  disadvantages  of  its  use. 

The  classification  of  methods  followed  is  based  upon  size 
of  deposit,  rather  than  kind  of  mineral  or  metal  and  char- 
acter of  deposit,  which  seems  the  simplest  and  most  logical 
method  of  treatment.  The  idea  has  been  to  describe  only 
those  methods  which  have  proved  successful  not  only  in  one 
locality  but  several,  and  not  to  consider  proposed  methods 
nor  those  in  the  experimental  stage. 

In  order  to  verify  descriptions  and  to  study  methods  more 
in  detail  the  writer  has  visited  the  mines  in  which  practically 


vi  PREFACE 

all  of  the  methods  described  are  employed;  however,  per- 
sonal inspection  has  been  confined  to  the  mines  of  the 
United  States. 

The  present  volume,  which  is  the  second  edition,  has  been 
completely  revised  and  much  new  material  has  been  added, 
including  a  chapter  on  development  of  mines.  Further,  ex- 
tensive use  of  photographs  of  models  has  been  made. 

Special  acknowledgment  of  suggestions  and  advice  is 
due  to  the  large  number  of  mining  men  who  have  extended 
many  courtesies  to  the  writer  while  collecting  the  informa- 
tion upon  which  the  work  is  based. 


WALTER  R.   CRANE. 


THE  PENNSYLVANIA  STATE  COLLEGE 
SCHOOL  OF  MINES,  Jan.  i,  1917. 


CONTENTS 


CHAPTER   I 

Support  of  Workings 

PAGE 

INTRODUCTION i 

METHODS  OF  SUPPORT 6 

PILLARS  OF  ORE  OR  WASTE  ROCK;  TIMBER  AS  MINE  SUPPORT;  PROPS; 
STULLS;  CRIBS  OR  BULKHEADS;  SQUARE-SETS;  FILLINGS  OF  ORE  OR 
WASTE;  SUPPORT  BY  INDIRECT  MEANS;  RESUME  —  PILLARS,  PROPS  OR 
POSTS,  STULLS,  CRIBS  OR  BULKHEADS,  SQUARE-SETS,  FILLING,  CAVING  25 

BIBLIOGRAPHY  OF  METHODS  OF  SUPPORT 25 

PILLARS,  TIMBERS,  CRIBS  FOR  MINE  SUPPORT,  SUBSIDENCE  AND  DOME 

OF  EQUILIBRIUM,  USE  OF  SCAFFOLDS  IN  MINES 27 


CHAPTER  II 
Development  of  Mines 

DEVELOPMENT  OF  MINES 28 

CONTROLLING  FACTORS;  USE  OF  VERTICAL  AND  INCLINED  SHAFTS,  USE 
OF  DRIFTS,  TUNNELS,  AND  SLOPES;  DEVELOPMENT  WITHIN  DEPOSIT; 

MAINTENANCE  OF  OUTPUT 48 

BIBLIOGRAPHY  OF  DEVELOPMENT  OF  MINES 48 

GENERAL,  DEVELOPMENT  OF  SUB-LEVEL  AND  SUB-DRIFT  METHODS  ....  50 


CHAPTER  III 
Methods  of  Stoping 

METHODS  OF  STOPING 51 

OVERHAND  STOPING;  UNDERHAND  STOPING;  COMBINED  STOPING;  BREAST 
STOPING;  SIDE  STOPING;  LONG  WALL  STOPING;  RESUING;  RESUME  OF  STOP- 
ING—  OVERHAND  STOPING,  UNDERHAND  STOPING,  BREAST  STOPING, 
OTHER  METHODS  OF  STOPING 73 

BIBLIOGRAPHY  OF  METHODS  OF  STOPING 73 

GENERAL,  OVERHAND  STOPING,  UNDERHAND  STOPING,  BREAST  STOPING, 

SHRINKAGE  STOPING,  RILL  STOPING,  RESUING 77 

vii 


viii  CONTENTS 

CHAPTER  IV 

Methods  of  Handling  Ore  in  Stopes 

PAGE 

METHODS  OF  HANDLING  ORE  IN  STOPES " 78 

HANDLING  ORE  IN  OPEN  STOPES,  HANDLING  ORE  IN  CLOSED  STOPES, 

CHUTES  AND  MILL-HOLES 91 

BIBLIOGRAPHY  OF  HANDLING  ORE  IN  MINES , 92 

GENERAL,  MILL-HOLES,  CHUTES  AND  CHUTE  GATES,  ORE  POCKETS, 
CHUTE  CONVEYORS  AND  PLANES 94 

CHAPTER  V 
Mining  in  Narrow  and  Moderately  Wide  Veins  and  Bedded  Deposits 

INTRODUCTION 95 

MINING  BEDDED  DEPOSITS  BY  THE  USE  OF  PROPS 96 

IRON  MINES  OF  THE  BIRMINGHAM  DISTRICT,  ALABAMA 96 

MINING  MINERAL  VEINS  BY  THE  USE  OF  STULLS 100 

TONOPAH  MINE,  TONOPAH,  NEVADA;  COMBINATION  MINE,  GOLDFIELD, 

NEVADA;  HECLA  MINE,  BURKE,  IDAHO 114 

MINING  MINERAL  VEINS  BY  THE  USE  OF  SQUARE-SETS 114 

THE  BUNKER  HILL-SULLIVAN  MINE,  WARDNER,  IDAHO 118 

MINING  MINERAL  VEINS  BY  THE  USE  OF  FILLING 119 

THE  ZARUMA  MINE,  ZARUMA,  ECUADOR;    THE  ST.  LAWRENCE  MINE, 

BUTTE,  MONTANA;  THE  BALTIC  AND  TRIMOUNTAIN  MINES,  MICHIGAN  133 

MINING  BEDDED  DEPOSITS  BY  CAVING 133 

MERCUR  AND  GOLDEN  GATE  MINES,  MERCUR,  UTAH 137 

CHAPTER  VI 
Methods  of  Mining  in  Wide  Veins  and  Masses 

INTRODUCTION 138 

SHRINKAGE  STOPING  METHODS  OF  MINING 140 

THE  GOLD  PRINCE  MINE,   ANIMAS  FORKS,  COLORADO;  THE  ALASKA- 

TREADWELL  MINES,  DOUGLAS  ISLAND,  ALASKA 150 

SQUARE-SET  METHODS  OF  MINING 150 

THE  MINES  AT  ROSSLAND,   BRITISH  COLUMBIA;  THE  QUEEN  MINE, 

NEGAUNEE,  MICHIGAN 155 

FILLING  METHODS 156 

THE  BROKEN  HILL  MINES,  N.  S.  W.;  THE  HOMESTAKE  MINE,  LEAD, 

SOUTH  DAKOTA 176 

CAVING  METHODS 1 76 

IRON  DEPOSITS  OF  THE  LAKE  SUPERIOR  REGION;  THE  MIAMI  MINE, 

ARIZONA;  THE  DIAMOND  MINES  OF  SOUTH  AFRICA 202 

BIBLIOGRAPHY  OF  METHODS 202 

SQUARE-SET  MINING,  FILLING  METHODS,  THE  CAVING  SYSTEMS 207 


CONTENTS  ix 

CHAPTER  VII 

Open-cut  Mining 

PAGE 

INTRODUCTION 208 

SURFACE  MINING  BY  HAND 210 

SURFACE  MINING  BY  SCRAPERS 215 

OPEN-CUT  MINING  BY  STEAM  SHOVEL 218 

THE  MILLING  METHOD 224 

BIBLIOGRAPHY  OF  OPEN-CUT  MINING  —  STEAM-SHOVEL  WORK,  GENERAL 

OPEN-CUT  WORK 235 

CHAPTER  VIII 
Cost  of  Mining 

INTRODUCTION 237 

DETAILED   DISCUSSION  OF  COST   OF  MINING  —  FUNDAMENTAL   ITEMS  OF 

COST,  LABOR,  SUPPLIES,  POWER,  LIGHT,  SUPPORT,  HANDLING 241 

GENERAL  MINING  COSTS  —  MINING  COSTS 247 

DETAILS  OF  MINING    COSTS  —  DEVELOPMENT,  STOPING,  SUPPORT 249 

COST  OF  OPEN-CUT  MINING 267 


LIST    OF    ILLUSTRATIONS 


FIGURE  PAGE 
Frontispiece 

1.  Corduroy  and  Filling  in  the  Comstock  Mines 2 

2.  Position  and  Use  of  Stull  in  Vein 10 

3.  Battery  Method  of  Stull  Timbering 10 

4.  Use  of  Square-sets,  Stulls  and  Filling 12 

5.  Use  of  Cribs  in  Filled  Stopes 14 

6.  Forms  of  Square-set  Framing 16 

7.  Square-sets  in  a  Large  Stope 18 

A.  Method  of  Timbering  Vertical  Stopes  with  Weak  Walls 24 

8.  Arrangement  of  Various  Development  Passages -. 31 

9.  Vertical  Section  through  Shaft  and  Orebodies  of  the  Alaska-Treadwell 

Mine 35 

10.  Plan  of  Development  on  Level  in  Sub-level  Method 44 

11.  Vertical  Section  through  Pillar  Showing  Development  Passages  and 

Chutes  for  Drawing  off  Ore 45 

12.  Overhand  Stoping,  'Breaking-through' 54 

13.  Methods  of  Stoping  and  Handling  Ore.     A  Composite  Sketch 56 

14.  Use  of  Stulls  and  Waste-filling 57 

15.  Underhand  Stoping  Methods  Showing  Wall  Pillars  and  Waste-stulls. ...  60 

16.  Plan  of  Underhand  Stoping  Workings  in  Massive  Deposit 61 

17.  Underhand  Stoping  in  'Sheet-ground/  Joplin  District. 

Conditions  Similar  to  Those  in  Massive  Deposits 62 

1 8.  Combined  Stoping  in  Moderately  Dipping  Vein 64 

19.  Ore-loading  Dock  in  Open  Stope 79 

20.  Loading  Cars  by  Chute,  Mohawk  Mine 81 

21.  Portion  of  Stope  Showing  Method  of  Handling  Soft  Ore 83 

22.  Block-hole  Fitted  with  Chute  for  Passing  Ore  through  Pillar 84 

23.  Use  of  Winged-stulls  in  Handling  Ore 86 

24.  Stope-chute  for  Handling  Excess  Ore  in  Stope 87 

25.  Chutes  Used  in  Developing  a  Shrinkage  Stope  with  Cribbed  Chute  and 

Manway 87 

26.  Broken-stope  Chute  and  Ore  Pocket  as  Used  in  the  Copper  Queen  Mine  89 

27.  A  Chinaman  Chute  as  Used  in  Australian  Mines 90 

28.  Chinaman  Ore  Chute  Provided  with  Grizzly 91 

B.  Chute  Used  for  Handling  Ore  in  the  Miami  Copper  Mine 91 

29.  Plan  of  Iron  Mine,  Birmingham  District,  Ala 99 

30.  Application  of  Stulls  to  Moderately  Wide  Veins 102 

31.  Use  of  Stulls  and  Stull-levels  in  Mining  Moderately  Wide  Veins 105 

xi 


xii  LIST  OF  ILLUSTRATIONS 

FIGURE  PAGE 

32.  Application  of  Stull-sets  to  the  Mining  of  Medium-sized  Veins 109 

33.  Plan  of  Second  Floor  of  Stull-set  Method no 

34.  Vertical  Section  through  Vein  Showing  Method  of  Placing  Stull-sets  ...  in 

35.  Plan  of  Second  Floor  in  Stull-set  Method 112 

36.  Square-set  Mining  in  Horizontal  Floors 116 

37.  Square-set  Mining  in  Inclined  Floors 118 

38.  Overhand  Stoping  in  Inclined  Floors  or  Rill  Stoping 120 

39.  Rill  Stoping  Showing  the  Use  of  Planks  on  Sloping  Bank  of  Waste-filling, 

also  Methods  of  Entering  Stopes  and  Disposal  of  Ore 122 

40.  Elevation  and  Plan  of  Stopes.     Back-filling  Method 124 

41.  Vertical    Section    through   Lode    Showing   Application   of   Back-filling 

Method 127 

42.  Passage  Formed  on  Level  by  'Rock- walls/  Showing  use  of  Waste  Rock 

and  Logs  in  Their  Construction,  etc 129 

43.  Baltic  and  Trimountain  Filling  Method 131 

44.  Transverse  Section  through  Deposit  Showing  Method  of  Developing 

Thick  Deposit 134 

45.  Longitudinal  Section  through  the  Sub-drifts  Showing  the  Incline  on  Right, 

also  other  Passages  Driven  Across  the  Deposit  from  the  Sub-drifts  .  .  136 

46.  Vertical  Section  through  Stope  Worked  by  Shrinkage  Method 139 

47.  Vertical  Longitudinal  Section  through  Lode  Showing  Method  of  De- 

velopment and  Working  by  Shrinkage  Stoping 141 

48.  Longitudinal  Section  through  Stope  Showing  Method  of  Working  by 

Shrinkage  Stoping 143 

49.  Vertical  Longitudinal  Section  through  Lode  and  Across  Stopes  Showing 

Development  Passages  and  Their  Relation  to  the  Stopes 145 

50.  Plan  of  Stopes  in  the  Alaska-Treadwell  Mines 146 

51.  Longitudinal  Section  through  Stopes  in  Alaska-Treadwell  Mines 148 

52.  Square-sets  Composed  of  Round  Timbers 150 

C.   Adaptation  of  Square-set  Mining  to  a  Highly  Inclined  Vein,  Showing  Ore 

Bin  and  Chute  for  Loading  Cars  on  Level 151 

53.  Square-set  Mining  in  Massive  Deposit 153 

54.  Square-set  Mining  in  Broken  Hill  Mines,  N.  S.  W 157 

55.  Plan  of  Square-set  Mining  in  Broken  Hill  Mines 159 

56.  Section  through  Lode,  Broken  Hill  Mines,  Showing  Open-stope  Method.  160 

57.  Cantilever-crib  in  Wide  Stope,  Australian  Mines 162 

58.  Plan  of  Pillar-and-stope  Method  in  Broken  Hill  Mines 163 

59.  Back-filling  Method  Used  in  Homestake  Mines 168 

60.  End  View  of  Stope  in  Homestake  Mine,  Back-filling  Method 170 

61.  Plan  of  Stopes  of  Back-filling  Method,  Homestake  Mines 173 

62.  Longitudinal   Section   through    Stopes   in   Homestake   Mines  —  Back- 

filling Method 175 

63.  Section  through  Vein,  Showing  Development  in  Top-slice  Method 178 

64.  Plan  and  Longitudinal  Section  of  Top-slice  Method 179 

65.  Transverse  Section  across  Lode  Showing  Method  of  Development  in 

Sub-drift  Method..  182 


LIST  OF  ILLUSTRATIONS  xiii 

FIGURE  PAGE 

66.  Longitudinal  Section  and  Plan  of  Sub-drift  Method 184 

67.  Vertical  Longitudinal  Section  through  Lode  Showing  Method  of  De- 

velopment and  Working  of  Sub-drift  Method 185 

68.  Plan  of  Block  of  Bad  Ground  Worked  by  Sub-drift  Method 187 

D.   Vertical  Longitudinal  Section  through  Body  of  Iron  Ore  Showing  Method 

of  Development  and  Working  of  Sub-drift  Method 188 

69.  Vertical  Section  across  Stopes  in  Shrinkage  Method  Employed  in  the 

Miami  Copper  Mine,  Arizona 190 

70.  Vertical  Longitudinal  Section  through  Pillar,  Showing  Method  of  Min- 

ing Pillars 192 

71.  Vertical  Section  through  Pipe,  Showing  Method  of  Working  by  Gal- 

leries, Diamond  Mines  of  South  Africa 197 

72.  Section  through  Pipe,  Showing  Method  of  Working  by  Caving 198 

73.  Plan  of  Pipe  and  Method  of  Development 196 

74.  Elevations  and  Plans,  Showing  Method  of  Opening  up  a  Stope 200 

75.  Sketch  Showing  Plan  of  Stopes  Run  Together 200 

76.  Vertical  Section,  Showing  Stopes  in  Various  Stages  of  Working 201 

77.  Mining  Bank  of  Shale  by  Hand 211 

78.  Quarry  Showing  Bench  before  Blast 213 

79.  Quarry  Showing  Result  of  Blast 214 

80.  Stripping  Coal  by  Scrapers 216 

81.  Section  across  Bingham  Canyon,  Showing  Beginning  of  Steam-shovel 

Work  in  Stripping  Capping 218 

82.  Steam-shovel  Mining  in  Soft  Iron  Ore  of  Birmingham  District,  Ala 220 

83.  Vertical  Section  through  Massive  Deposit  of  Iron  Ore,  Showing  Method 

of  Development  and  Working  by  Milling  Method 226 

84.  The  Still-room-milling  Method 224 


ORE  MINING  METHODS 


CHAPTER   I 
SUPPORT  OF   WORKINGS 

INTRODUCTION 

METHODS  of  mining  and  support  of  workings  are  so 
closely  related  that  the  discussion  of  one  necessitates  a 
more  or  less  detailed  treatment  of  the  other.  It  therefore 
seems  eminently  proper  and  even  necessary  to  preface  a 
work  of  this  character  with  a  brief  discussion  regarding  the 
elements  of  support.  A  description  of  the  elemental  units 
of  support,  such  as  pillars,  props,  cribs,  stulls  and  square- 
sets  will  not  therefore  be  out  of  place  in  this  connection. 
Further,  the  use  of  filling  is  considered,  as  it  is  rapidly 
becoming  an  important  factor  in  the  support  of  under- 
ground excavations;  caving  as  a  factor  in  support  is  also 
discussed. 

While  no  particular  knowledge  regarding  methods  of 
support  other  than  may  be  found  in  the  following  pages  is 
essential  to  a  full  and  complete  understanding  of  the  con- 
tents of  this  work,  yet  a  working  knowledge  of  support  of 
excavations  will  not  come  amiss,  and  such  knowledge  is 
assumed  to  be  possessed  by  the  intelligent  reader  of  this 
work. 


2  ORE   MINING   METHODS 

To  the  careful  observer  it  is  becoming  more  and  more 
evident  that  timber  cannot  be  relied  upon  to  support  mine 
workings  as  mining  is,  and  must  of  necessity  be,  carried  on 
today.  With  the  constantly  decreasing  value  of  the  mineral 
content  of  the  ores  of  many  mines  and  the  opening  up  of 
enormous  deposits  of  low-grade  ores,  the  demand  is  becom- 
ing more  urgent  for  decreased  costs  of  working  or  extracting 


FIG.  i. —  Corduroy  and  Filling  in  the  Comstock  Mines. 

the  ores.  Contemporaneously  with  this  general  trend  of 
affairs  has  occurred  a  scarcity,  in  many  localities,  of  a  suit- 
able supply  of  timber  at  reasonable  rates.  The  result  has 
been,  then,  that  with  no  other  available  material  at  hand 
that  was  cheaper,  methods  requiring  a  minimum  amount 
of  timber  were  resorted  to,  and  as  a  further  advancement 
filling  and  caving  methods  are  rapidly  coming  into  general 
use  and  are  supplanting  the  older  and  more  expensive 
methods  where  much  timber  is  used.  As  the  methods  of 


SUPPORT   OF  WORKINGS  3 

working  mineral  deposits  have  then  yielded  to  the  demands 
of  economy,  in  like  manner  the  old  type  of  conservative 
mine  superintendent  is  giving  way  to  the  ingenious,  ener- 
getic and  efficient  modern  mining  engineer,  whose  slogan  is 
"  increased  tonnage  at  decreased  costs.'7 

Further,  aside  from  the  question  of  economy  the  mining 
engineer  has  long  since  learned  that  timber  or  any  other 
similar  form  of  support  must  be  considered  as  temporary 
only  when  we  come  to  maintaining  openings  at  a  depth  of 
several  thousand  feet.  To  attempt  to  support  a  mountain 
by  timber  or  even  pillars  of  ore  or  rock  is  but  to  invite  in  the 
course  of  time  disastrous  caves  with  the  possible  resulting 
loss  of  life  and  property.  The  extremes  gone  to  in  an 
endeavor  to  hold  back  loose  or  swelling  ground  is  well 
illustrated  by  the  close-set  cribbing  or  corduroy  employed 
in  the  bonanza  days  on  the  Comstock  Lode  and  still  used 
there  in  isolated  places.  (See  Fig.  i.)  The  veritable  forest 
of  closely  placed  props  to  be  seen  in  many  of  our  metal 
mines,  and  the  stulls  of  three  or  four  feet  in  diameter  em- 
ployed in  the  lower  levels  of  the  deep  copper  mines  of 
Keweenaw  Point,  Michigan,  all  attest  the  ever-present  and 
constantly  growing  need  of  a  radical  change  in  methods  of 
procedure  in  supporting  workings  made  for  the  economic 
extraction  of  mineral. 

While  the  application  of  rock-filling  to  the  support  of 
mine  workings  is  by  no  means  recent  in  the  mines  of  the 
United  States,  yet  its  rapid  extension  to  a  majority  of  the 
metal  mining  districts,  irrespective  of  the  kind  of  metal 
mined,  has  taken  place  within  the  last  ten  years.  By  rock- 


4  ORE  MINING   METHODS 

filling,  as  referred  to  above,  is  meant  a  filling  of  waste,  the 
excavations  receiving  little  or  no  other  support  except  of 
the  most  temporary  character.  Filling  in  connection  with 
square-sets  has  been  used  extensively  in  the  mines  of  this 
country  ever  since  its  application  to  the  mines  of  the  Corn- 
stock  Lode. 

Aside  from  the  question  of  an  available  supply  of  suitable 
material  for  filling  there  are  certain  objections  to  its  use, 
some  of  which  are  so  serious  as  to  preclude  its  employment 
except  under  prescribed  and  limiting  conditions. 

Probably  the  principal  disadvantages  are  shrinkage  of  the 
mass  of  filling  and  a  tendency  to  become  ' quick'  and  flow. 
The  former  action  leads  to  movements  which  although 
gradual  are  nevertheless  pronounced  and  may  result  in 
serious  disarrangement  of  the  workings,  shafts,  levels,  etc., 
and  may  lead,  under  certain  conditions,  to  the  flooding  of 
the  workings.  However,  under  normal  conditions,  these 
disadvantages  may  be  insignificant  compared  with  the 
benefits  resulting  from  its  use.  The  latter  disadvantage 
while  always  present  is  accentuated  only  when  the  filling 
employed  is  mixed  with  a  certain  amount  of  earthy  or  clayey 
material  and  becomes  charged  or  saturated  with  water. 
Further,  the  practice,  often  a  necessity,  of  using  the  filling 
over  and  over  again  tends  to  render  it  less  suitable  for  the 
work  owing  to  the  constantly  increasing  proportion  of  fine 
material  produced  by  the  attrition  of  the  moving  mass  of 
filling,  when  drawn  from  one  part  of  the  workings  to  another, 
and  the  accumulation  of  gouge  and  muck  left  from  the  mining 
operations. 


SUPPORT  OF  WORKINGS  5 

It  is  not,  however,  so  much  the  seriousness  of  the  dis- 
advantages as  it  is  the  lack  of  control  of  the  actions  leading 
thereto.  It  may  be  said  without  hesitation  that,  where 
conditions  are  favorable,  such  as  a  moderately  strong  ore 
supporting  itself  sufficiently  well  to  permit  introducing  and 
spreading  the  filling  without  interference  with  temporary 
supports,  together  with  a  suitable  filling  and  plenty  of  it 
readily  available,  the  filling  methods  have  proved  and  are 
proving  amply  adequate.  When  such  general  conditions 
do  not  prevail  and  suitable  timber  at  reasonable  rates  is 
not  available,  some  other  method  not  dependent  upon  such 
factors  must  be  resorted  to.  The  caving  methods  might 
then  well  be  employed. 

Caving  is  confined  to  ore  bodies  of  considerable  size, 
especially  of  horizontal  extent,  and  to  ores  of  a  fairly  uni- 
form mineral  content,  its  application  being  gradually  ex- 
tended to  districts  where  other  methods  of  mining  have  long 
been  in  use.  Often  where  square-setting,  with  or  without 
filling,  was  formerly  exclusively  employed,  caving  has  now 
taken  its  place  wholly  or  in  part  or  a  combination  of  the  two 
is  resorted  to.  Caving  is  usually  employed  only  where 
other  methods  are  inapplicable  and  inadequate.  Its  use 
means  large-scale,  continuous  and  rapid  work,  with  a  con- 
sequently large  tonnage  and  small  expense  per  ton. 

Caving  is  not  synonymous  with  scant  use  of  timber;  on 
the  contrary  a  large  amount  of  timber  may  be  required  as 
when  the  sub-drift  system  is  used,  but  as  the  timber  is  for 
temporary  use  only,  being  often  of  inferior  quality  and  used 
in  the  rough,  the  expense  may  be  considerably  less  than  a 


6  ORE   MINING   METHODS 

more  permanent  method  of  support  where  less  timber  is 
employed.  What  timber  support  is  used  serves  mainly  for 
protection  to  the  miners  who  as  parts  of  an  intelligent 
system  are  directing  and  utilizing  the  tremendous  force  of 
the  superimposed  mass  of  loose  and  broken  rock  and  ore 
which  is  slowly  but  irresistibly  following  the  withdrawal  of 
the  ore  downward. 

METHODS  OF  SUPPORT 

The  means  of  supporting  mine  workings  may  be  outlined 
as  follows: 

1 .  Pillars  of  ore  or  waste  rock. 

2.  Timbering,  consisting  of  props,  stulls,  cribs  and  square- 
sets. 

3.  Fillings  of  ore  or  waste;  the  former  temporary,  the 
latter  permanent. 

4.  Support  by  indirect  means,  i.e.,  by  arching  the  work- 
ings and  by  caving  methods,  where  the  ore  to  be  mined  takes 
the  load  temporarily,  being  reenforced  by  timber. 

Pillars  of  Ore,  or  Waste  Rock.  —  Pillars  were  naturally 
first  employed  in  the  support  of  workings  underground,  and 
will  always  be  used  instead  of  artificial  support  except  when 
their  use  means  the  permanent  curtailment  of  the  output 
of  the  mine,  or  when  they  are  less  stable  and  durable  than 
other  available  supports. 

The  chief  objection  to  the  use  of  pillars,  aside  from  the 
loss  of  valuable  mineral,  is  that  it  is  difficult  to  ensure  their 
proper  formation  and  location.  To  secure  the  maximum 
benefit  of  supports  of  any  kind  requires  that  they  should  be 


SUPPORT  OF  WORKINGS  7 

symmetrically  and  systematically  placed,  a  thing  that  is  next 
to  impossible  to  obtain  in  the  case  of  pillars  underground. 
Either  there  will  be  ore  occurring  at  the  place  where  a  pillar 
should  logically  come  or  some  irregularity  of  or  in  the  deposit 
will  influence  a  change  in  location  and  result  in  a  serious 
irregularity  of  the  system  adopted.  In  like  manner  the 
shape  of  the  pillar  may  be  changed;  instead  of  a  square  or 
rectangular  section  with  ends  flaring  slightly  at  both  top  and 
bottom,  where  connection  is  made  with  the  hanging  and  foot 
walls,  the  sections  are  more  usually  roughly  round  or  ellipti- 
cal, while  the  general  appearance  resembles  an  hourglass.  . 

The  pernicious  habit  of  gradually  cutting  away  pillars 
to  secure  a  few  more  tons  of  ore  results  in  producing  most 
grotesque  shapes  and  an  alarming  condition  of  support. 
Pillars  standing  12  to  15  feet  high,  in  moderately  inclined 
deposits,  are  not  infrequently  reduced  from  a  diameter  of 
1 6  to  20  feet  at  the  top  and  bottom  to  4  and  often  3  feet  at 
the  middle,  and  in  certain  observed  instances  to  i  foot 
diameter  at  the  'waist  line.7  Such  pillars  soon  deteriorate 
under  the  enormous  weight  thrown  upon  them  and  show 
signs  of  distress  by  vertical  cracks  extending  from  top  to 
bottom.  The  caved  stopes  of  the  upper  levels  of  the  large 
copper  mines  of  the  Lake  Superior  region  bear  witness  to  the 
fact  that  inefficient  support  in  the  shape  of  ill-formed  pillars 
is  both  inadequate  and  futile. 

Pillars  are  named  according  to  the  position  they  occupy 
with  respect  to  the  stope;  those  at  the  top  of  the  stope 
are  known  as  'arch'  pillars,  those  next  to  the  shaft  are 
'shaft'  pillars,  while  those  occupying  various  positions  in 


8  ORE   MINING   METHODS 

the  stope  are  usually  known  as  'wall'  pillars.  A  special 
form  of  wall  pillar  is  the  so-called  'dead-end,'  a  pillar  ex- 
tending the  whole  height  of  the  stope  and  spaced  at  inter- 
vals of  about  200  feet  along  the  stope.  (See  Fig.  13.) 

Timber  as  Mine  Support.  -  -  Timber  well  adapted  to  use 
in  underground  work  is  becoming  somewhat  scarce  in  many 
localities  in  the  United  States.  Oak  is  excellent  but  is 
rarely  used  owing  to  its  scarcity.  On  the  Pacific  coast  the 
cone-bearing  or  coniferous  trees  are  widely  used.  Of  the 
thirty-six  varieties  found  there  the  most  important  are: 
the  Oregon  pine,  spruce,  yellow  pine,  tamarack,  sugar  pine, 
pinion  or  bull  pine,  besides  several  varieties  of  fir  and  red- 
wood. In  Washington  and  many  of  the  Western  states 
the  Oregon  pine  is  extensively  used  for  both  mine  and 
surface  work  and  is  known  in  different  localities  by  various 
names,  such  as,  Douglas  fir,  Douglas  spruce,  yellow  fir  or 
red  fir,  while  in  the  parlance  of  the  lumbermen  it  is  known 
as  Oregon  pine  and  Puget  Sound  pine.  Yellow  pine  al- 
though of  no  great  durability  or  strength  is  widely  used. 

Fir  is  quite  strong,  as  is  pine  also,  the  softer  woods  having 
the  advantage  over  the  harder  in  that  they  crush  more 
readily,  thus  taking  up  the  load  more  uniformly. 

Props  or  posts  may  be  considered  as  the  principal  element 
in  mine  timbering,  being  employed  in  connection  with  nearly 
all  forms  of  timbering  under  certain  conditions.  Props  and 
posts  may  be  round  or  square  and  are  set  normal  to  the  roof 
and  floor  of  the  workings.  They  have  their  widest  range  of 
usefulness  in  flat  or  slightly  inclined  deposits  and  are  there- 
fore especially  applicable  to  bedded  deposits.  In  order  to 


SUPPORT  OF  WORKINGS 


increase  the  bearing  surface  caps  are  often  provided,  which 
consist  of  short  lengths  of  plank  placed  between  the  ends  of 
the  props  and  roof  or  floor. 

Stulls  while  performing  the  same  function  as  props  and 
posts  are  used  only  in  more  or  less  highly  inclined  deposits, 
having  their  widest  range  of  usefulness  in  narrow  veins, 
say  up  to  15  ft.  in  width.  Stulls  are,  however,  used  in 
veins  of  35  to  40  ft.  in  width,  and  for  inclinations  up  to 
90°,  or  the  vertical.  The  application  of  stulls  is  considerably 
different  from  that  of  props  owing  to  conditions  brought 
about  by  change  in  dip  of  the  deposit.  Like  the  prop  or 
post  the  stull  often  has  a  cap  used  with  it,  but  it  is  placed  at 
the  upper  end  only,  the  lower  end  being  set  into  a  notch  or 
'  hitch '  cut  into  the  lower  or  foot  wall  of  the  vein  and  wedged 
tight.  The  object  of  the  hitch  is  to  prevent  the  timber 
slipping  from  its  place.  Further,  stulls  are  not  set  normal  to 
the  walls  of  the  vein  but  in  such  a  position  that  their  devia- 
tion from  the  normal,  called  '  angle  of  underlie, '  is  about 
one-fourth  that  of  the  angle  of  dip  of  the  deposit,  thus: 


Dip  of  Vein 

Angle  of  Underlie 
of  Stull 

Dip  of  Vein 

Angle  of  Underlie 
of  Stull 

10° 

2i° 

40° 

10° 

20° 

5° 

5°° 

I2j° 

30° 

7*° 

60° 

15° 

The  reason  for  setting  stulls  at  an  angle  with  the  walls 
instead  of  normal  to  them  is  to  ensure  against  their  becom- 
ing loose  and  falling  out  of  place,  which  would  surely  result 
if  they  were  set  normal  and  a  movement  of  the  walls  should 


10 


ORE  MINING  METHODS 


FIG,  2.  —  Position  and  Use  of  Stull  in  Vein. 


FIG.  3.  —  Battery  Method  of  Stull  Timbering. 
(Modeled  after  Sketch  by  Claude  T.  Rice.) 


SUPPORT  OF  WORKINGS  n 

take  place.  When  set  at  an  angle  any  downward  move- 
ment of  the  hanging  wall  serves  only  to  set  the  stull  more 
firmly  in  the  hitch.  (See  Fig.  2.) 

Stulls  are  extensively  employed  at  the  foot  of  s topes  in 
veins  of  steep  or  moderately  steep  inclinations  and  serve 
both  as  a  protection  to  the  levels  and  as  a  support  for  the 
ore  or  waste  that  is  placed  upon  them.  Stulls  when  covered 
with  lagging  may  serve  as  platforms  upon  which  drills  may 
be  mounted  in  the  work  of  stoping.  In  steep  veins,  inter- 
mediate levels  or  floors  may  be  formed  at  intervals  of  15  or 
20  ft.,  by  rows  of  stulls,  lagged  and  covered  with  ore  or 
waste,  the  stoping  of  the  ore  extending  horizontally  and 
vertically  from  the  level  so  formed  until  sufficient  room  is 
made  for  another  row  of  stulls  to  be  placed.  Waste-covered 
stulls  are  usually  designated  as  '  waste-stulls.'  (See  Fig.  13.) 

It  is  often  necessary  to  reenforce  stulls,  which  is  usually 
done  by  placing  several  below  the  one  to  be  reenforced. 
The  auxiliary  stulls  may  be  placed  directly  below  or  grouped 
together  forming  the  so-called  '  battery  of  timbers  '  or  stulls. 
Still  another  modification  in  the  use  of  stulls  is  where  they 
are  used  in  conjunction  with  square-sets,  long  stulls  often 
being  employed  in  holding  the  square-sets  in  place  when  for 
certain  reasons  it  is  not  considered  necessary  or  desirable  to 
fill  the  stope  with  sets.  The  stulls  serve  in  reality  as  elon- 
gated caps  in  the  system  of  square-sets.  (See  Figs.  3  and  4.) 

Props  or  struts  and  stulls  are  occasionally  used  together, 
especially  when  long  stulls  are  necessary,  the  struts  being  set 
in  between  the  stulls  to  hold  them  in  place,  thus  steadying 
them  and  preventing  buckling. 


12 


ORE  MINING  METHODS 


SUPPORT  OF  WORKINGS  13 

Cribs  or  Bulkheads  are  usually  composed  of  damaged 
timber,  old  ties,  props  and  stulls,  put  together  in  pigsty 
fashion,  two  or  more  timbers  being  placed  parallel  one  with 
the  other  and  then  bound  together  by  other  timbers  laid 
across  their  ends  and  middle,  which  operation  is  continued 
until  the  roof  or  hanging  wall  is  reached,  when  they  are 
wedged  fast.  In  order  to  make  these  constructions  more 
stable  they  are  often  filled  with  waste.  Cribs  filled  with 
waste,  or  otherwise,  probably  have  their  widest  range  of 
usefulness  in  the  mining  of  coal,  but  are  often  employed  in 
wide  stopes  where  ordinary  methods  of  support  are  inade- 
quate and  where  a  certain  amount  of  room  for  mining  and 
handling  the  ore  is  available.1  Cribs  in  combination  with 
filling,  being  built  in  the  stopes  during  the  extraction  of  the 
ore  and  then  buried  in  filling  when  the  stope  is  abandoned, 
give  added  strength  and  stability  to  the  filling.  (See  Fig.  5.) 

Square-sets  have  been  very  extensively  employed  in  the 
metal  mines  of  the  United  States  and  are  still  used  to 
the  exclusion  of  other  methods  in  certain  districts.  While 
especially  applicable  to  wide  veins  of  moderately  steep  in- 
clinations, square-sets  are  often  used  in  veins  from  15  to  20 
ft.  in  width,  and  in  exceptional  cases  to  much  greater  widths. 

In  placing  square-sets  the  usual  practice  is  to  begin  at  the 
bottom  of  a  stope  or  a  level  and  lay  long  sill  timbers  which 
are  regularly  spaced  by  other  timbers,  thus  covering  the 
floor  of  the  open  stope  with  a  system  of  timbers  arranged  in 

1  Cribs  are  extensively  used  in  the  mines  of  Broken  Hill,  South  Australia, 
where  cribs  without  filling  are  called  'horses,'  while  those  with  rilling  are 
designated  as  'pigstyes.' 


14  ORE  MINING  METHODS 

squares.     Upon  these  timbers  are  erected  other  timbers 
which  consist  of  posts,  caps  and  girts  or  ties.     The  posts 


FIG.  5.  —  Use  of  Cribs  in  Filled  Stopes. 
(Modeled  after  Sketch  by  H.  L.  Hancock,  Wallaroo  Mines,  South  Australia.) 

are  placed  upright  at  the  intersection  of  the  sills  and  cross- 
pieces,  and  upon  the  posts  are  placed  caps,  the  ends  of  which 
rest  on  two  adjacent  posts  in  a  direction  transverse  with 


SUPPORT  OF  WORKINGS  15 

the  vein.  The  girts  also  rest  upon  the  posts  but  run  longi- 
tudinally with  the  vein.  The  caps  and  girts  when  in  place 
form  a  new  level  or  floor,  and  by  successive  additions  of 
posts,  caps  and  girts  the  timber  support  can  be  kept  within 
easy  reach  of  the  walls  or  roof  of  the  stope.  In  like  manner 
by  the  addition  of  sills  the  sets  can  be  extended  indefinitely 
in  either  direction  along  the  vein  or  deposit.  A  plat- 
form or  staging  as  well  as  support  is  thus  provided  for  any 
portion  of  the  roof  or  sides  of  the  stope.  The  stopes  are 
then  filled  with  a  cellular  mass  of  timbering  perfectly 
matched  together  and  symmetrical  in  all  directions. 

In  order  that  the  various  members  of  the  square-sets  may 
fit  together  and  be  in  perfect  alinement,  the  posts  standing 
vertically  and  the  caps  and  girts  lying  horizontally,  it  is 
necessary  that  they  be  cut  to  gauge,  and  the  ends  formed  so 
as  to  both  hold  the  members  in  place  and  provide  a  perfectly 
fitting  joint.  Further,  the  ends  of  the  different  timbers  are 
so  cut  that  the  largest  cross-sectional  area  is  opposed  to  the 
greatest  pressure,  as  in  the  case  of  the  caps  which  are  placed 
normal  to  the  walls.  While  there  are  a  large  number  of 
different  forms  of  joints  suitable  to  framing  both  sawed  and 
round  timber,  yet  the  details  given  in  Fig.  6  illustrate 
very  well  two  methods  of  framing  that  are  widely  used. 
Where  the  ground  is  particularly  heavy,  diagonal  braces 
are  placed  in  the  sets  and  in  line  with  the  greatest 
pressure. 

The  length  of  the  posts  varies  largely  with  the  locality, 
but  as  a  rule  the  first  set  of  posts,  and  in  fact  the  posts  at 
any  level,  where  hauling  is  done  in  cars,  are  sufficiently  high 


i6 


ORE  MINING  METHODS 


SUPPORT  OF  WORKINGS  17 

to  permit  the  passage  of  men.  The  usual  length  of  posts 
is  6  to  8  ft.  in  the  clear,  the  caps  and  girts  being  about  5 
to  6  and  4  to  6  ft.  respectively. 

As  timber  became  more  difficult  to  secure  for  the  mines 
the  first  and  most  natural  expedient  was  to  modify  the  con- 
struction of  the  square-sets  by  using  rough  round  instead  of 
sawed  timber  and  the  employment  of  longer  posts.  Round 
timber  while  being  somewhat  more  difficult  to  frame  is  con- 
siderably stronger  than  the  sawed  forms.  Thus  the  result 
is  decreased  cost  and  increased  strength. 

Increased  length  of  posts  also  decreases  the  cost,  but  there 
is  a  definite  limit  in  this  direction  if  strength  and  rigidity 
of  support  are  desiderata.  A  further  modification  is  the 
variation  in  size  of  the  different  members  of  the  sets,  the 
posts,  caps  and  girts  being  of  different  cross-sectional 
dimensions. 

Experience  has  shown  that  it  is  not  so  much  the  depth 
with  consequent  increase  in  pressure  as  the  strength  and 
firmness  of  the  walls  that  determine  the  usefulness  and 
safety  of  square-sets  as  support  for  workings.  This  was 
demonstrated  in  the  mines  of  the  Comstock  Lode,  where 
the  support  of  the  upper  workings  was  often  fully  as  difficult 
as  in  other  localities  at  greater  depth.  Further,  there  is  a 
limit  in  height  to  which  square-sets  can  be  used,  beyond 
which  the  timbers  will  crush  under  their  own  weight.  The 
limit  in  the  Homestake  mines,  South  Dakota,  ranges  between 
80  and  90  ft.  It  is  then  evident  that  when  square-sets  are 
employed  the  height  of  the  stopes  should  not  exceed  100  ft. 
Use  of  square-sets  in  a  gold  mine  is  shown  in  Fig.  7. 


i8 


ORE   MINING   METHODS 


SUPPORT  OF  WORKINGS  19 

From  the  standpoint  of  economy  the  use  of  square-sets 
is  hardly  warrantable,  although  there  are  instances  where 
owing  to  the  occurrence  of  cheap  timber  it  may  prove  to 
be  the  most  economical  method  that  can  be  employed. 

Fillings  of  Ore  or  Waste.  —  Filling  methods  have  been 
successfully  employed  for  many  years  in  the  mines  of  this 
country  and  are  rapidly  being  extended,  especially  the  use  of 
waste.  The  filling  of  underground  excavations,  as  stopes, 
with  ore  is  a  method  employed  for  reasons  of  utility  and 
economy  as  well  as  support.  Ore  may  be  located  and 
broken  in  the  stopes  but  not  drawn  off,  except  as  is  found 
necessary  to  provide  room  for  the  operation  of  stoping.  As 
there  is  an  increase  in  volume  of  from  30  to  40  per  cent  in 
broken  ore,  it  is  evident  that  a  certain  amount  must  be 
drawn  off  after  each  round  of  shots  to  give  space  for  sub- 
sequent work  at  the  face.  A  large  amount  of  ore  may  then 
remain  in  the  mine,  forming  an  'ore  reserve.'  The  advan- 
tages of  such  a  system  are:  a  large  force  of  men  may  be 
employed  in  breaking  ore;  less  danger  from  falls  of  rock 
owing  to  rapidity  of  working;  reduced  cost  of  breaking  and 
handling  ore;  a  more  uniform  output;  and  a  more  careful 
grading  of  ores  resulting  from  not  having  to  rush  work  in 
order  to  keep  up  with  the  required  output. 

The  work  at  the  face  is  materially  facilitated  by  this 
method  of  procedure,  as  the  ore  serves  as  a  platform  upon 
which  the  drills  are  mounted,  the  height  of  which  may  be 
varied  at  will.  The  ore  while  stored  in  the  stopes  also  serves 
as  a  support  for  the  workings,  reducing  or  eliminating  the 
support  that  would  otherwise  be  necessary.  It  is  difficult  to 


20  ORE  MINING  METHODS 

imagine  a  case  where  ore  would  be  introduced  into  a  mine 
or  transferred  to  any  part  of  it  for  support,  owing  to  the 
extra  cost  involved,  as  well  as  the  loss  in  fine  ore  resulting 
from  attrition  in  handling.  The  principal  reason  for  leav- 
ing ore  in  stopes  is  the  establishment  of  an  ore  reserve, 
although  occasionally  low-grade  ore  may  be  held  in  the 
stopes  until  such  a  time  as  it  can  be  treated  with  profit. 
Further,  the  temporary  need  of  support  maybe  so  urgent  that 
it  is  expedient  to  resort  to  the  use  of  even  a  fair  grade  of  ore. 
The  use  of  waste  in  the  support  of  underground  workings 
is  now  a  well-established  method,  and  its  widespread  appli- 
cation indicates  how  favorably  it  is  looked  upon  by  mining 
men.  The  employment  of  waste-filling  depends  to  a  large 
extent  upon  its  source.  There  are  three  possible  sources  of 
waste,  namely :  that  resulting  from  mining  operations,  being 
sorted  from  the  ore  or  portions  of  the  walls  that  have  to  be 
broken  down  in  cutting  out  the  ore;  that  obtained  from 
special  excavations  made  in  the  vein  walls,  usually  the  hang- 
ing-wall; and  material  from  quarries  or  open-cuts  on  the 
surface  and  the  waste  products  from  concentrating  works, 
such  as  tailings.  The  first  source  mentioned  is  the  most 
important,  as  comparatively  little  labor  is  required  in  placing 
it  properly  in  the  excavation  to  be  supported.  This  is 
particularly  true  in  the  case  of  veins  where  but  a  small  part 
of  the  ore  is  valuable,  the  bulk  of  the  vein-content  being 
used  as  filling;  also  in  certain  cases  where  more  waste  is 
required  than  can  be  obtained  from  sorting  the  ore,  the 
additional  amount  is  secured  by  blasting  several  feet  off 
the  walls.  Much  filling  is  now  taken  from  the  surface 


SUPPORT  OF  WORKINGS  21 

and  by  the  use  of  waste  chutes  is  conducted  to  any  portion 
of  the  mine  desired,  being  distributed  by  cars.  Under- 
ground excavations  opened  especially  to  secure  waste  for 
filling  are  occasionally  made,  but  it  is  a  method  of  procedure 
which  is  liable  to  lead  to  disastrous  results,  as  in  starting 
caves,  unless  the  ground  is  particularly  strong. 

Support  by  Indirect  Means.  —  Indirect  methods  are  re- 
sorted to  wherever  intelligent  supervision  is  given  to  the 
work  and  where  conditions  are  favorable.  The  natural  arch 
formed  by  caving  ground,  or  the  so-called  'dome  of  equi- 
librium,' may  be  employed  to  advantage  in  the  temporary 
support  of  underground  excavations.  The  i  fracture  pris- 
moid'  is  another  name  for  the  same  phenomenon.  By  arch- 
ing the  roof  it  is  often  possible  to  maintain  it  without 
any  support  or  with  very  temporary  constructions.  The 
character  of  the  ground  is  the  governing  factor  in  this 
work,  certain  formations  not  being  sufficiently  strong  to 
stand  even  with  short  spans  and  high  arches,  while  other 
specially  strong  formations  may  be  given  exceedingly  long 
spans  and  low  arches.  The  wide  stopes  of  the  Homestake 
and  Alaska-Treadwell  mines  illustrate  remarkably  well  the 
application  of  the  '  dome  of  equilibrium '  to  strong  and  stable 
formations. 

Caving  may  be  employed  as  a  supplementary  method 
following  some  well-defined  system,  usually  with  timber 
supports,  until  its  limit  of  applicability  has  been  reached  or 
exceeded.  The  weight  of  the  unmined  ore  together  with  the 
mass  of  broken  waste  and  timber  lying  above  the  ore  is 
temporarily  supported  by  pillars  of  ore  and  timber.  In  the 


22  ORE  MINING  METHODS 

course  of  time  the  pillars  begin  to  break  up,  and  by  care- 
fully and  systematically  removing  the  timber  supports  and 
attacking  the  pillars  in  such  a  manner  as  to  assist  the  dis- 
integration, practically  all  of  the  ore  remaining  above  the 
level  worked  may  be  drawn  off  with  little  or  no  danger  to  the 
laborers  or  the  integrity  of  mine  workings. 

The  support  of  the  caving  ore  and  overlying  caved 
material  is  of  the  most  temporary  character  and  really 
amounts  to  a  well-defined  and  scientific  control  of  the  move- 
ment of  the  caving  mass  rather  than  its  definite  support. 

In  order  that  the  methods  of  support  discussed  above  may 
be  rendered  still  more  comprehensive  the  following  brief 
statements  are  made  regarding  their  application  and  com- 
parative advantages  and  disadvantages. 

Pillars  of  mineral  constitute  the  most  natural  form  of 
support  for  underground  workings.  The  advantages  in  their 
use  are :  the  vein-content  left  in  place  is  probably  the  strong- 
est possible  support  obtainable;  support  can  be  provided 
at  any  desired  point;  there  is  no  expense  attendant  upon 
their  use  and  no  risk  from  fire.  The  disadvantages  are :  loss 
of  mineral  when  formed  in  ore;  a  tendency  to  make  them  too 
small  to  save  ore;  also  a  like  tendency  and  for  similar  reasons 
to  place  them  irregularly  or  dispense  with  them  altogether. 

Props  or  Posts  can  be  used  to  advantage  in  a  vertical  or 
nearly  vertical  position  only.  Their  chief  advantage  lies  in 
the  ease  with  which  they  can  be  placed  and  removed  if 
desired. 

Stulls  have  a  very  much  wider  range  of  application  than 
posts,  as  they  can  be  employed  in  veins  ranging  from  an 


SUPPORT  OF  WORKINGS  23 

inclination  of  about  10°  to  the  vertical.  When  properly 
placed  they  are  not  affected  by  slight  movements  of  the 
walls  and  are  therefore  suitable  for  a  great  variety  of  con- 
ditions. They  may  be  employed  as  supports  of  scaffoldings 
upon  which  drills  are  mounted,  forming  '  stull-levels '  and 
'  waste-stulls. ' 

Cribs  or  Bulkheads  owing  to  their  width  are  more  stable 
than  posts  or  stulls,  but  to  give  the  best  results  must  be 
built  practically  vertical.  They  cannot  be  used  to  advan- 
tage except  in  horizontal  or  slightly  inclined  deposits  or  wide 
veins.  While  readily  built  they  are  difficult  to  take  down, 
especially  when  filled  with  waste,  and  occupying  considerable 
space  encumber  the  workings,  interfering  with  handling  ore 
and  supplies. 

Square-sets  like  cribs  must  be  built  along  horizontal 
and  vertical  lines  and  are  therefore  confined  to  compara- 
tively wide  veins  and  massive  deposits.  They  are  expensive 
to  frame  and  place  and  unless  filled  with  waste  soon  buckle 
and  crush,  both  under  their  own  weight  and  that  of  the  walls. 
However,  for  the  support  of  large  openings  they  have  proven 
indispensable  in  the  past,  the  ease  with  which  extensions  can 
be  made  in  any  direction  being  a  most  important  factor  in 
mining. 

Filling  mine  workings,  especially  with  waste,  is  growing 
in  favor  owing  to  the  fact  that  support  can  be  placed 
quickly  and  readily;  the  waste  of  the  mine  can  be  disposed 
of  at  minimum  expense,  and  cheap  material  can  be  trans- 
ferred underground  with  little  work;  it  can  be  used  a  num- 
ber of  times,  being  drawn  from  one  part  of  the  mine  to 


24  ORE  MINING  METHODS 

another;    a  good  support  uniformly  distributed  over  the 
walls  is  obtained,  and  there  is  no  fire  risk. 

The  disadvantages  resulting  from  the  use  of  filling  are 
shrinkage  of  filling  disturbing  workings  and  a  tendency  for 
the  filling  to  become  quick  and  flow  under  pressure. 


A.  —  Method  of  Timbering  Vertical  Stopes  with  Weak  Walls. 
(Modeled  after  Sketch  by  H.  H.  Hodgkinson.) 


Caving  as  an  indirect  method  of  support  is  applicable  to 
large  deposits  only;  requires  continuous  and  rapid  work; 
the  loss  of  mineral  may  be  considerable  owing  to  the  move- 


SUPPORT  OF  WORKINGS  25 

ment  of  the  caving  mass  getting  beyond  control;  and  a  large 
amount  of  timber  is  required  with  certain  deposits.  The 
advantages  and  disadvantages  are:  a  large  output  at  mod- 
erate cost;  operations  must  begin  near  the  surface;  and  the 
overlying  rock  must  cave  readily. 

BIBLIOGRAPHY  OF  METHODS  OF  SUPPORT 

The  following  references  are  given  in  order  that  what  is  actually  done  in 
practice  may  be  shown  rather  than  what  might  seem  desirable  from  the 
theoretical  standpoint. 

PILLARS 

The  Witwatersrand  Gold  Fields,  by  S.  J.  Truscott,  p.  346;  Ibid.,  p.  335. 

Mining  Copper  Ore  at  Lake  Superior,  by  Claude  T.  Rice.  Eng.  and  Min- 
ing Jour.,  vol.  94,  p.  405;  Ibid.,  vol.  94,  p.  267. 

Ore  Breaking  at  Lake  Superior,  by  W.  R.  Crane.  Eng.  and  Mining  Jour., 
vol.  82,  p.  767. 

Departure  in  Sheet-ore  Mining  in  the  Joplin  District,  by  Temple  Chapman. 
Eng.  and  Mining  Jour.,  vol.  87,  p.  942. 

Cananea  Caving  and  Slicing  Systems,  by  R.  L.  Herrick.  Mines  and 
Minerals,  vol.  30,  p.  23. 

Mining  Methods  Employed  at  Cananea,  Mexico,  by  Morris  J.  Elsing. 
Eng.  and  Mining  Jour.,  vol.  90,  p.  963. 

TIMBERS 

Practical  Rules  for  Cutting  Mine  Timber,  by  Bernard  Carr.     Mining  and 

Scientific  Press,  vol.  no,  p.  409. 
Iron  Mining  in  the  Birmingham  District,  Ala.,  by  W.  R.  Crane.     Eng. 

and  Mining  Jour.,  vol.  79,  p.  274. 
Davis  Pyrites  Mine,  Massachusetts,  by  J.  J.  Rutledge.     Eng.  and  Mining 

Jour.,  vol.  82,  p.  673. 

The  Combination  Mine,  Nevada,  by  Edgar  A.  Collins.     Mining  and  Scien- 
tific Press,  vol.  95,  p.  435. 
Battery  Method  of  Stull  Timbering,  by  Claude  T.  Rice.    Eng.  and  Mining 

Jour.,  vol  93,  p.  255. 
Buffalo  Mine  and  Mill,  Cobalt,  by  W.  J.  Dobbins  and  H.  G.  S.  Anderson. 

Eng.  and  Mining  Jour.,  vol.  94,  p.  211. 
Finger-pin  Timbering  in  Swelling  Ground.    Eng.  and  Mining  Jour.,  vol. 

93,  P- 349- 


26  ORE  MINING  METHODS 

A  Method  of  Underhand  Sloping,  by  Geo.  A.  Laird.     Eng.  and  Mining 

Jour.,  vol.  92,  p.  945. 
Timbering  Stopes  for  Safety,  by  H.  H.  Hodgkinson.     Eng.  and  Mining 

Jour.,  vol.  99,  p.  818. 
A  Method  of  Mining  hi  Heavy  Ground,  by  W.  L.  Fleming.     Eng.  and 

Mining  Jour.,  vol.  88,  p.  375. 
Increasing  the  Use  of  Steel  Supports  for  Mines,  by  Frank  H.  Wagner. 

Mining  and  Scientific  Press,  vol.  no,  p.  372. 
Metal  Drift  Set.     Eng.  and  Mining  Jour.,  vol.  95,  p.  518. 
Steel  Mine  Timbers,  by  R.  B.  Woodworth.     Published  by  the  Carnegie 

Steel  Company. 
Methods  of  Iron  Mining  in  Northern  Minnesota,  by  F.  W.  Denton.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  27,  p.  344. 

CRIBS  FOR  MINE  SUPPORT 

Timbering  Wide  Stopes,  by  H.  L.  Hancock.    Eng.  and  Mining  Jour.,  vol. 

88,  p.  376. 
The  Mount  Morgan  Mine,  Central  Queensland,  by  J.  Bowie  Wilson.     Eng. 

and  Mining  Jour.,  vol.  87,  p.  746. 
Stoping  Systems  at  Broken  Hill,  Australia,  by  A.  J.  Moore.     Mines  and 

Minerals,  vol.  27,  p.  433. 
Stoping  Methods  at  the  Nevada  Wonder  Mine,  by  Thomas  M.  Smither. 

Mining  and  Scientific  Press,  vol.  no,  p.  757. 

SUBSIDENCE  AND  DOME  OF  EQUILIBRIUM 

Mine  Subsidence,  by  Alex  Richardson.    Jour.  Chem.  Metallurgical  and 

Mining  Soc.  of  South  Africa,  vol.  7,  p.  325. 
The  Dome  of  Equilibrium  and  the  Caving  System  of  Mining,  by  Claude 

T.  Rice.     Mining  and  Scientific  Press,  vol.  95,  p.  85. 
The  Rill  System  of  Stoping,  by  J.  Bowie  Wilson.     Eng.  and  Mining  Jour., 

vol.  92,  p.  1000. 
Method  of  Mining  Swedish  Iron  Ore,  by  H.  de  Rauw.     Eng.  and  Mining 

Jour.,  vol.  91,  p.  409. 
Mining  the  Treadwell  Lode,  by  T.  A.  Rickard.     Mining  and  Scientific 

Press,  vol.  97,  p.  85. 

USE  OF  SCAFFOLDS  IN  MINES 

Portable  Scaffold  for  Mine  Use.     Eng.  and  Mining  Jour.,  vol.  89,  p.  404. 
Method  of  Rigging  Ladders  to  Reach  Stope  Backs.     Eng.  and  Mining  Jour., 
vol.  89,  p.  357. 


SUPPORT  OF  WORKINGS  27 

Portable  Scaffold  for  Drilling  High  Roof,  by  Wm.  M.  McKearin.     Eng. 

and  Mining  Jour.,  vol.  95,  p.  371. 

Mining  a  Pillar  of  Iron  Ore.     Eng.  and  Mining  Jour.,  vol.  94,  p.  879. 
Trimming  Roofs  of  High  Slopes,  by  Claude  T.  Rice.     Eng.  and  Mining 

Jour.,  vol.  94,  p.  629. 
Scaffolding  in  an  Untimbered  Raise,  by  Frank  C.  Rork.    Eng.  and  Mining 

Jour.,  vol.  96,  p.  20. 

For  use  of  square-sets  see  Square-Set  Mining. 
For  references  to  the  use  of  filling  and  caving  methods,  see  page  202. 


CHAPTER  II 
DEVELOPMENT  OF  MINES 

Mining  operations  may  be  roughly  grouped  into  three 
classes,  namely:  exploration,  development,  and  working. 
Each  of  these  operations  is  in  most  cases  necessary  and 
required  if  a  property  is  to  be  properly  prepared  for  sys- 
tematic and  economical  production  of  ore,  except  possibly 
where  the  occurrence  of  the  ore  is  well  known  and  previous 
operations  in  the  district  have  developed  and  established  a 
satisfactory  practice.  In  such  cases  it  is  often  possible  to 
eliminate  or  materially  reduce  exploration  and,  to  a  less 
extent,  development  work,  although  it  must  always  be  kept 
in  mind  that  the  mining  risk  is  ever  present  and  that  unex- 
pected conditions  may  be  encountered  at  any  time.  By 
development  work  the  'ore  reserve'  is  established,  assuring 
a  regular  and  continuous  output,  which  with  large  opera- 
tions is  not  only  desirable  but  necessary. 

By  exploration  is  meant  the  search  for  and  location  of 
orebodies  and  it  consequently  precedes  development  work. 
Prospecting  is  the  first  stage  of  exploratory  work  and  con- 
sists in  the  use  of  ditches  crossing  the  outcrop  of  veins,  test 
pits  sunk  in  the  deposit,  bore  holes  usually  placed  normal  to 
the  dip  of  the  deposit,  and  under  certain  circumstances 
short  drifts,  slopes  or  inclines  and  shallow,  vertical  shafts 

may  be  used  which  latter  work  is  more  properly  called  ex- 

28 


DEVELOPMENT  OF  MINES  29 

ploration.  It  is  evident,  then,  that  there  is  no  sharp  line 
separating  prospecting  from  exploration  nor  exploration 
from  development  work  and  in  a  similar  way  development 
work  merges  into  the  breaking  down  of  the  ore  or  the  working 
of  the  mine. 

The  development  of  a  mine  consists  in  connecting  the 
deposit  with  the  surface  by  means  of  .passages  suitable  for 
the  handling  of  ore  and  supplies,  for  the  going  and  coming 
of  men,  for  ventilation  and  drainage,  and  in  fact  for  all  of 
the  operations  necessary  for  the  working  of  the  mine. 

At  the  completion  of  development  work  the  mine  is  as- 
sumed to  be  in  condition  for  the  economic  extraction  of 
ore  and  should  be  fully  equipped  for  that  purpose;  drills 
and  all  machinery  necessary  for  the  breaking  of  ore  and 
transferring  it  to  the  surface;  equipment  for  drainage  and 
in  some  cases  for  ventilation  should  be  installed  during 
development  work  and  should  be  so  designed  as  to  permit  of 
additions  with  minimum  work  and  expense  incident  upon 
the  growth  and  expansion  of  the  mine  workings. 

Aside  from  opening  mineral  deposits  and  preparing  them 
for  the  breaking  of  ore  and  its  transference  to  the  surface, 
the  establishment  of  an  'ore  reserve'  is  an  important  con- 
sideration. Except  in  the  case  of  small  mines  and  irregular 
operations,  or  where  the  ore  is  placed  in  stockpiles  (which 
are  in  fact  ore  reserves)  it  is  generally  considered  desirable 
to  form  an  ore  reserve  in  the  mine.  The  object  of  an  ore 
reserve  is  to  provide  a  definite  amount  of  ore  which  is  held 
in  reserve  and  can  be  drawn  upon  as  occasion  demands. 
There  are  two  forms  of  ore  reserves,  namely,  'ore  blocked 


30  ORE  MINING  METHODS 

out '  and  '  ore  broken  down ' ;  the  former  ensures  a  constant 
supply  of  probably  workable  ore  for  a  definite  period  and 
thereby  tends  to  reduce  the  '  mining  risk, '  the  latter  provides 
a  fixed  tonnage  to  be  drawn  upon  to  maintain  the  uniform 
output  of  the  mine.  The  ore  reserve  is  therefore  an  effective 
means  of  establishing  and  maintaining  stability  in  mining 
operations  and  if  formed  during  the  development  period, 
or  the  early  stages  of  opening  mines,  may  materially  reduce 
the  expense  of  such  work  and  enhance  the  value  of  mining 
properties. 

Controlling  Factors.  —  Before  proceeding  with  the  details 
of  the  methods  of  development  it  might  be  well  to  outline 
briefly  the  factors  that  determine  in  a  general  way  the  choice 
of  methods,  which  are  as  follows: 

1.  Physical    characteristics    and    primary    irregularities 
of  deposits. 

2.  Secondary  irregularities  due  to  earth  movements. 

Under  physical  characteristics  may  be  listed:  the  con- 
dition of  the  ore,  shape  and  size  of  the  deposit,  character  of 
top  and  bottom  rock  or  hanging-  and  foot- walls,  position  of 
deposit  with  respect  to  surface,  and  distance  from  surface. 

The  primary  irregularities  consist  of  change  of  the  thick- 
ness of  deposit,  occurrence  of  interstratified  bands  of  impu- 
rities, and  the  presence  of  irregular  masses  of  foreign  material. 

Irregularities  of  deposits  due  in  large  part  to  conditions 
affecting  deposition  or  the  formation  of  deposits  may  materi- 
ally affect  the  method  of  development  and  consequently 
the  method  of  mining,  but  usually  require  a  modification 
rather  than  a  change  in  method. 


DEVELOPMENT  OF  MINES  31 

On  the  other  hand,  irregularities  arising  from  earth  move- 
ments are  of  considerable  consequence  and  often  require 
radical  changes  in  both  the  scheme  of  development  adopted 
and  subsequently  the  method  of  mining  employed.  The 
two  most  important  irregularities  and  the  onry  ones  that 


FIG.  8. — Arrangement  of  Various  Development  Passages. 


need  be  mentioned  in  this  connection  are  folding  and  fault- 
ing, the  effect  of  which  is  most  pronounced  in  bedded 
deposits.  By  folding  of  horizontally  lying  strata,  variations 
of  dip  are  produced  as  exemplified  in  anticlines,  synclines, 
and  basins;  while  by  faulting,  which  is  a  direct  result  of 
folding,  fissures  are  produced  and  by  subsequent  movement 
such  irregularities  as  thickening  and  thinning  of  vein-con- 


32  ORE  MINING  METHODS 

tent,  branching  of  veins,  occurrence  of  barren  masses  of 
rock  or  'horses,'  scattering  of  values,  and  displacement  of 
portions  of  veins,  are  of  common  occurrence. 

Aside  from  being  the  controlling  factor  in  choice  of  the 
preliminary  opening,  as  drift,  tunnel,  slope  or  vertical  and 
inclined  shafts,  the  dip  also  determines  the  location  of  the 
opening  with  respect  to  hanging-  and  foot- walls  and  in  the 
case  of  basins  with  respect  to  the  lowest  point,  as  drainage 
as  well  as  haulage  must  be  considered.  The  presence 
of  faults  complicates  such  conditions  but  seldom  requires  a 
radical  alteration  of  methods. 

A  working  knowledge  of  the  laws  governing  faults  is 
desirable  but  not  absolutely  necessary  if  one  is  concerned 
in  the  development  of  deposits  occurring  in  a  locality  where 
faults  exist;  however,  the  best  possible  guide  is  the  experi- 
ence gained  from  actual  operations  in  the  field  and  the 
results  of  such  experience  should  be  carefully  examined 
when  available. 

The  shape  of  deposits  and  the  dip  are  of  the  first  im- 
portance from  the  standpoint  of  development  and  are 
largely  independent  of  whether  the  deposits  are  bedded  or 
occur  in  veins.  For  instance  a  massive  deposit  may  result 
from  the  folding  of  a  bed  or  the  impregnation  of  the  walls  of 
a  vein  or  a  line  of  contact  of  different  formations ;  or  a  bedded 
deposit  may  be  to  all  intents  and  purposes  a  vein  when  it 
stands  at  a  fairly  high  inclination,  or  the  enriched  portions 
of  beds  and  veins  may  be  similar  in  occurrence  and  due  in 
part  to  the  same  cause;  and,  lastly,  the  phenomena  of  thick- 
ening and  thinning  of  deposits,  also  the  splitting  up  into 


DEVELOPMENT  OF  MINES  33 

one  or  more  parts,  are  characteristic  of  beds  and  veins, 
although  due  to  different  causes. 

Use  of  Vertical  and  Inclined  Shafts.  —  Massive  deposits  re- 
quire different  methods  of  procedure  in  development  than 
do  bedded  deposits  or  veins,  although  thick  beds  and  massive 
deposits  may  under  certain  circumstances  be  developed 
according  to  the  same  general  plan.  Massive  deposits  are 
usually  developed  in  floors,  while  steeply  dipping  bedded 
deposits  and  veins  are  developed  in  levels,  which  are  in  fact 
relatively  narrow  floors.  As  a  rule,  massive  deposits  are 
opened  by  vertical  shafts,  although  it  may  be  desirable 
owing  to  the  peculiar  shape  of  a  deposit  to  employ  an 
inclined  shaft  for  its  development. 

Inclined  bedded  deposits  and  veins  afford  a  wide  range 
of  choice  of  methods  of  development,  subject,  however,  to 
the  conditions  imposed  by  the  inclination  or  dip.  In  a 
general  way  it  may  be  said  that  deposits  lying  at  some 
distance  from  the  surface  with  their  axes  in  a  horizontal 
plane,  or  approximately  so,  should  be  developed  by  means  of 
vertical  shafts  if  possible,  otherwise  by  inclined  shafts. 
Highly  inclined  beds  and  veins  are  developed  by  inclined  and 
vertical  shafts,  except  where  it  is  possible  to  employ  drifts 
and  tunnels  due  to  outcrops  occurring  on  the  slopes  of  hills 
and  mountains,  or  where  the  deposit  is  so  situated  as  to 
be  readily  reached  by  a  tunnel.  Slopes  should  be  employed 
in  developing  slightly  inclined  deposits  dipping  into  the 
hill  from  the  outcrop.  (See  Fig.  8.) 

While  there  is  no  sharp  line  drawn  in  practice  in  the 
designation  by  means  of  angle  of  dip  of  slopes  and  inclined 


34  ORE  MINING  METHODS 

shafts,  yet  it  is  desirable  that  limits  should  be  set,  which  may, 
however,  be  varied  to  suit  the  practice  in  different  districts. 
The  limits  set  by  common  practice  are  as  follows: 

•  Angle  Made  with  Horizontal 

Drift  or  tunnel o°  to  3° 

Slope  or  plane 3°  "  25° 

Inclined  shaft 25°  "  85° 

Vertical  shaft 90° 

Except  in  rare  cases  there  can  be  no  doubt  as  to  choice  of 
a  drift,  tunnel  or  slope,  but  with  inclined  and  vertical  shafts, 
or  when  highly  inclined  deposits  are  to  be  developed,  there 
may  be  some  doubt  as  to  which  would  be  better.  In  certain 
districts  practice  favors  inclined  shafts,  while  in  other  dis- 
tricts vertical  shafts  are  used  exclusively.  A  careful  study 
of  existing  conditions  will,  however,  usually  disclose  the 
underlying  reasons,  which  may  not  be  generally  recognized. 

In  development,  as  in  all  other  operations,  cost  is  often 
the  determining  factor,  and  in  this  work  in  particular  both 
first  and  operating  costs  must  be  considered.  Owing  to  the 
large  amount  of  dead  work  necessary  to  reach  the  deposits 
by  means  of  cross-cuts  driven  from  vertical  shafts,  there  is 
a  limit  beyond  which  such  work  is  not  permissible.  The 
limit  has  been  determined  by  practice  to  be  when  the  de- 
posit stands  at  an  inclination  of  36°  with  the  horizontal. 

Vertical  shafts  are  usually  not  in  the  deposit  but  when 
possible  are  placed  in  the  foot-wall  and  at  some  distance 
from  the  outcrop.  Veins  with  inclinations  of  36°  and 
upward  usually  have  the  shaft  located  on  the  hanging-wall 
side,  thus  subdividing  the  deposit  into  two  portions  of  ap- 
proximately the  same  dimensions  vertically  with  relatively 


DEVELOPMENT  OF  MINES  35 

the  same  amount  of  development  work  in  each.     Further, 
the  longer  dimension  of  the  cross-section  of  *theT shaft  should 


FIG.  9.  —  Vertical  Section  through  Shaft  and  Orebodies  of  the  Alaska-Treadwell 
Mines.    (Modeled  after  Sketch  in  Mining  and  Scientific  Press,  Feb.  10,  1917.) 

be  normal  to  the  outcrop  for  the  reason  that  the  shaft  will 
be  less  subject  to  disturbance  arising  from  movements  in 
the  walls  of  the  deposit.  (See  Fig.  9.) 


36  ORE  MINING  METHODS 

As  indicated  above,  connection  is  made  with  the  deposit 
by  cross-cuts  or  passages  driven  through  the  enclosing  rock 
and  connecting  the  shaft  and  deposit;  at  the  points  of  in- 
tersection of  the  cross-cuts  and  deposit,  passages  are  driven 
forming  the  so-called  levels,  thus  dividing  the  deposit  into 
blocks  of  convenient  size  for  the  extraction  of  ore. 

The  advantages  resulting  from  the  use  of  vertical  shafts 
are  as  follows: 

1.  Vertical  shafts  are  more  permanent  in  character  and 
less  affected  by  removal  of  ore  than  are  other  openings,  with 
the  possible  exception  of  tunnels. 

2.  The  distance  to  deposit  is  usually  less  than  in  the  case 
of  tunnels. 

3.  Vertical  shafts  are  more  readily  supported  than  are 
other  forms  of  openings  and  the  cost  of  material  is  less. 

4.  The  wear  of  hoisting  rope  is  considerably  less  than  when 
haulage  is  done  in  horizontal  passages  or  on  inclined  planes. 

5.  Ultimately  vertical  shafts  are  employed  in  working 
deep-seated    deposits    and    development  work    should    be 
planned  accordingly. 

The  principal  disadvantages  of  vertical  shafts  are  as 
follows : 

1.  They  are  more  difficult  to  sink. 

2.  No  cost  is  defrayed  until  development  is  practically 
completed. 

3.  No  information  is  obtainable  regarding  the  deposit 
until  a  late  date. 

Inclined  shafts  may  be  sunk  within  or  without  the  de- 
posit, either  adjacent  to  the  foot- wall  side  or  in  the  foot- 


DEVELOPMENT  OF  MINES  37 

wall  itself.  If  the  vein  filling  is  strong  it  is  preferable  to 
place  the  shaft  in  the  deposit  and  next  to  the  foot-wall,  un- 
less it  is  desired  to  remove  the  whole  of  the  deposit,  in  which 
case  no  shaft  pillars  are  left  and  the  shaft  is  driven  in  the 
foot-wall  and  at  a  safe  distance  from  the  deposit.  The 
same  method  of  procedure  may  be  followed  when  the 
wall-rock  and  ore  are  heavy  and  weak. 
The  advantages  in  the  use  of  inclined  shafts  are: 

1.  They  are  somewhat  easier  to  sink  than  are  vertical 
shafts. 

2.  Work  in  the  deposit  can  begin  immediately  and  the 
ore  obtained  during  development  will  in  part  defray  the 
expense.     To  render  a  mine  productive  during  the  early 
stages    of   development,    inclined    shafts    should   be    em- 
ployed. 

3.  Information  regarding  character  of  deposit  and  oc- 
currence of  ore  is  available  at  any  time. 

The  disadvantages  of  inclined  shafts  are: 

1.  They  are  not  as  permanent  as  vertical  shafts. 

2.  They  are  more  difficult  to  support  than  vertical  shafts. 

3.  Hoisting  and  handling  of  ore  is  not  so  readily  ac- 
complished nor  as  safe  as  with  vertical  shafts. 

4.  While  less  power  is  required  in  hoisting  the  wear  of 
rope  is  greater  in  inclined  shafts. 

The  fact  that  ore  may  be  produced  practically  at  the 
beginning  of  development  work  together  with  the  added 
advantage  of  more  rapid  work  in  sinking  due  to  softer 
formations  and  better  working  conditions,  make  the  use 
of  inclined  shafts  more  acceptable  for  the  initial  and  pre- 


38  ORE  MINING  METHODS 

liminary  openings  in  steep  and  moderately  steeply  dipping 
deposits. 

The  combination  of  inclined  and  vertical  shafts  or  the  so- 
called  ' turned- vertical'  shafts  are  common  and  result  from 
certain  occurrences  of  formation  as  well  as  working  con- 
ditions ;  for  instance,  where  inclined  beds  or  veins  terminate 
in  fault  planes,  or  where  through  folding,  beds  or  veins  re- 
verse their  dip,  and  where  the  outcrop  of  deposit  occurs  off 
the  property  or  is  too  far  distant  to  permit  of  development 
by  inclined  shafts.  Turned-vertical  shafts  possess  prac- 
tically all  of  the  advantages  of  inclined  and  vertical  shafts 
and  on  the  other  hand  have  few  of  the  disadvantages  of 
either  considered  separately. 

Use  of  Drifts,  Tunnels,  and  Slopes.  —  The  use,  as  well  as 
the  advantages  and  disadvantages  of,  inclined  and  vertical 
shafts  have  been  discussed,  but  no  statement  aside  from 
that  giving  limiting  degrees  of  dip,  has  been  made  regard- 
ing the  use  of  other  development  openings.  (See  Fig.  8.) 

In  order  that  there  may  be  no  misunderstanding  re- 
garding the  use  of  the  various  openings  employed  in  the 
development  of  mines,  the  following  definitions  are  given : 1 

1.  A  drift  is  a  passage  practically  horizontal,  begun  on  the 
outcrop  and  lying  wholly  within  the  deposit. 

2.  A  tunnel  is  a  passage  of  slight  grade  driven  from  the 
surface  across  bedding  planes  to  the  deposit.     The  original 
idea  of  a  tunnel  was  that  of  a  passage  extending  through  a 

1  Owing  to  the  number  of  passages  often  required  for  the  development  of 
an  orebody  the  distinguishing  characteristics  noted  cannot  be  held  to  in 
all  cases,  which  is  particularly  true  regarding  drifts  and  cross-cuts. 


DEVELOPMENT  OF   MINES  39 

hill  or  mountain  from  daylight  to  daylight,  but  according 
to  present  practice,  only  one  end  of  the  tunnel  needs  to 
reach  the  surface. 

3.  An  adit  or  adit-level  is  a  passage  nearly  level  which 
may  or  may  not  follow  the  deposit  and  which  is  intended  to 
be  used  wholly  or  in  part  as  a  drainage  opening. 

It  is  evident  that  with  deposits  dipping  into  a  hill  or 
mountain  side  or  away  from  the  outcrop,  any  passage  driven 
within  them  for  development  purposes  will  of  necessity 
have  a  grade  the  reverse  of  that  given  to  the  various  open- 
ings mentioned  above,  and  that  such  openings  cannot  be 
employed  for  drainage  purposes. 

Beginning  with  the  opening  of  lowest  dip  and  consequently 
that  nearest  in  grade  to  the  drift,  tunnel  or  adit,  and  pro- 
ceeding upward  to  the  vertical,  we  have  the  slope  or  incline, 
the  inclined  shaft  and  the  vertical  shaft. 

Slopes  and  inclines  are  operated  as  engine  or  gravity 
planes,  while  inclined  shafts  are  equipped  in  practically  the 
same  manner  as  vertical  shafts  as  the  weight  of  the  load  is 
thrown  in  large  measure  upon  the  hoisting  rope.  In  the 
former  case,  several  cars  are  employed  in  transferring  the 
ore  from  the  mine  to  the  surface,  while  in  the  latter  case 
skips  holding  from  a  few  to  as  many  as  twenty  tons  are 
used  singly,  which  on  high  dips  must  be  prevented  from 
overturning  by  guides,  thus  resembling  cages  used  in  vertical 
shafts. 

Brief  comparative  statements  regarding  the  use  of  the 
various  forms  of  development  openings  are  given  as  fol- 
lows: 


40  ORE  MINING  METHODS 

1.  Drifts,  slopes,  or  inclined  shafts  when  driven  in  the 
deposit  have  the  following  advantages: 

a.  The  cost  is  less  as  the  deposit  is  usually  easier  to 

work  than  the  enclosing  rocks. 

b.  Mineral  extracted  often  pays  a  large  part  of  the  ex- 

pense of  opening. 

c.  Valuable  information  is  obtained  regarding  thick- 

ness, shape,  size,  and  extent  of  deposit.     Further, 
there  is  little  danger  of  losing  vein. 

d.  Work  of  breaking  ground  can  begin  at  an  early  date. 

2.  The  use  of  a  drift  may  be  preferable  to  that  of  a  slope 
or  shafts  for  the  following  reasons : 

a.  It  is  cheaper  to  drive  a  passage  than  sink  a  shaft: 

ratio  1-3. 

b.  It  is  easier  to  drive  a  passage  than  to  sink  a  shaft: 

ratio  1-5. 

c.  A  drift  is  self-draining,  thus  the  operating  cost  is 

lessened. 

d.  Hauling  is  cheaper  than  hoisting. 

3.  The  advantages  of  a  drift  may  be  secured  by  the  use 
of  a  tunnel,  particularly  from  the  standpoint  of  handling 
mineral  and  supplies,  ventilation,  drainage,  etc.,  although 
a  tunnel  cannot  be  driven  as  readily  as  it  crosses  bedding 
planes.     Further,    there   are   no   immediate   returns   from 
mineral  mined,  thus  delaying  the  paying  time  of  the  mine, 
nor  is  any  information  available   regarding   the   deposit. 
A  tunnel  may,  however,  be  a  good  means  of  search  for 
mineral  deposits,  but  may  fail  to  discover  an  orebody  due 
to  crossing  the  vein  at  a  barren  point. 


DEVELOPMENT  OF  MINES  41 

4.  Vertical  shafts  are  in  some  respects  better  than  drifts, 
tunnels,  and  slopes  for  the  following  reasons: 

a.  Distance  to  deposit  is  usually  less  than  with  tunnel, 

thus  reducing  the  cost  of  development  work. 

b.  The  amount  of  timber  used  in  support  is  relatively 

small  and  the  cost  is  therefore  less  than  with 
other  openings. 

c.  Vertical   shafts   are   more   permanent   than   drifts, 

tunnels,  and  slopes. 

d.  The  amount  of  rope  required  is  relatively  small 

and  the  wear  is  correspondingly  less. 

On  the  other  hand,  shafts  are  more  difficult  to  sink,  no  cost 
is  defrayed  during  development  work,  and  no  information 
regarding  the  deposit  is  obtainable  until  it  is  reached. 

Development  within  Deposit. -- The  methods  by  which 
deposits  can  be  reached  and  connection  made  with  the  sur- 
face as  through  drifts,  tunnels,  slopes,  shafts,  etc.,  have 
been  discussed,  but  there  still  remain  to  be  considered 
the  methods  of  preparing  deposits  of  different  size,  shape, 
and  inclination  for  the  work  of  breaking  and  removing  the 
ore. 

Bedded  deposits  and  veins  may  be  considered  as  similar 
from  the  standpoint  of  development  within  the  deposit, 
with  the  possible  exception  of  horizontally  lying  deposits, 
when  a  somewhat  different  method  of  procedure  will  be 
necessary.  Very  large  veins,  zones,  and  massive  deposits 
may  also  be  considered  as  similar.  Orebodies  may,  for 
purposes  of  development,  be  divided  into  two  classes,  namely 
veins  and  massive  deposits. 


42  ORE  MINING  METHODS 

Veins  when  opened  by  drifts,  slopes,  and  shafts  lying  in 
the  deposit  give  the  simplest  possible  method  of  develop- 
ment, for  all  that  is  necessary  is  to  connect  such  openings 
with  passages  driven  in  the  deposit  at  more  or  less  fixed 
distances  apart,  vertically,  thus  subdividing  the  deposit 
into  blocks  or  zones  which  may  be  attacked  from  one  or 
more  directions,  or  by  workings  driven  up  or  down  the  dip. 
The  more  usual  method  is  to  begin  the  work  of  breaking 
ore  from  below,  thus  taking  advantage  of  gravity  in  drilling, 
blasting,  and  handling  the  ore.  (See  Fig.  8.) 

If  the  preliminary  opening  is  an  inclined  or  vertical  shaft 
not  within  the  deposit,  intermediate  connecting  passages 
must  be  driven  to  the  deposit,  from  which  in  turn  the  hori- 
zontal passages  in  the  deposit  are  driven  as  in  the  former 
case.  The  intermediate  passages  are  known  as  cross-cuts 
and  it  is  the  driving  of  such  passages  that  constitutes  the 
limiting  conditions  in  the  use  of  vertical  shafts  as  previously 
pointed  out. 

The  horizontal  or  slightly  inclined  passages  driven  in 
the  vein  and  connecting  with  the  preliminary  development 
openings  are  commonly  designated  as  levels,  differing  from 
drifts  in  that  they  do  not  reach  the  surface.  These  hori- 
zontal passages  are  in  turn  connected  with  each  other  by 
other  passages  within  the  deposit  and  run  at  right  angles 
to  them,  thus  blocking  out  the  ore  and  rendering  it  acces- 
sible to  the  miner  and  at  the  same  time  giving  a  means  of 
determining  the  value  of  the  ore  thus  blocked  out.  Ore 
so  blocked  out  is  commonly  spoken  of  an  an  'ore  reserve' 
and  differs  from  the  ' broken  ore  reserve'  in  that  its  value  is 


DEVELOPMENT  OF  MINES  43 

not  definitely  known  and  further  has  to  be  mined  before  it 
becomes  available  for  removal  from  the  mine  for  transpor- 
tation to  the  mill  or  smelter. 

Passages  connecting  levels  are  designated  as  raises  or 
winzes,  depending  upon  whether  they  are  driven  upward 
or  sunk;  they  are  both  shafts,  in  fact,  driven  from  points 
within  the  mine  rather  than  from  the  surface. 

Massive  deposits  and  large  veins  are  also  developed  by 
drifts,  tunnels,  shafts,  etc.,  the  choice  of  preliminary  open- 
ing depending  largely  upon  the  depth  of  deposit  from  the 
surface  and  its  position  with  respect  to  the  surface.  When 
once  connected  with  the  surface  either  by  levels  in  the 
deposit  or  by  cross-cuts  through  the  enclosing  rock,  the 
orebody  is  cut  up  into  horizontal  blocks  by  a  system  of 
passages  on  the  respective  levels  and  does  not  differ  essen- 
tially from  similar  work  in  veins,  except  that  there  are  of 
necessity  a  larger  number  of  passages  on  each  level  arranged 
so  as  to  facilitate  the  handling  of  empty  and  loaded  cars. 

With  veins  and  relatively  small  bedded  deposits  the 
working  places  or  stopes  run  longitudinally  with  the  deposit, 
while  with  the  massive  orebodies  and  wide  veins  the  stopes 
are  usually  run  transversely,  pillars  and  stopes  extending 
from  foot-  to  hanging-wall  and  spaced  at  regular  intervals 
along  the  greater  dimension  of  the  deposit. 

Large  outputs  require  provision  to  be  made  for  handling 
large  tonnages  and  consequently  a  definite  and  well-de- 
veloped system  of  haulage  ways  must  be  maintained,  with 
adequate  means  of  drawing  the  ore  from  the  stopes  to 
points  in  the  haulage  ways  where  it  is  loaded  into  cars. 


44 


ORE  MINING  METHODS 


1  Branched-'  or  l broken-chutes,'  '  winged-stulls/  steel  chutes, 
shaking  conveyors  and  a  system  of  haulage  ways  that  permit 
of  handling  ingoing  empty  and  outgoing  loaded  cars  without 
interference  are  essential  parts  of  the  system  of  development 
that  permit  of  large  scale  operations  as  are  necessary  with 


FIG.  10.  —  Plan  of  Development  on  Level  in  Sub-Level  Method. 
(Modeled  after  Sketch  by  Frank  Kennedy.) 

the  employment  of  filling  and  caving  methods.     (See  Figs. 
10  and  n.) 

A  well-developed  vein  or  highly  inclined  bedded  deposit 
may  be  likened  to  a  high  building,  narrow  but  long,  the 
floors  of  which  are  served  by  an  elevator.  Massive  deposits 
may  similarly  be  likened  to  a  factory  covering  considerable 
area,  the  floors  of  which  are  also  served  by  one  or  more 


DEVELOPMENT  OF  MINES 


45 


elevators  with  well-defined  passages  for  handling  cars  or 
trucks  as  well  as  for  the  passage  of  laborers.  In  a  similar 
manner  a  horizontal  bedded  deposit  of  moderate  thickness 


Fia.  ii.— Vertical  Section  through  Pillar  Showing  Development  Passages  and 
Chutes  for  Drawing  off  Ore.     (Modeled  after  Sketch  by  T.  D.  Tallant.) 

when  developed  resembles  the  streets  of  a  city  and  not 
only  with  respect  to  the  working  places  in  the  buildings  and 
the  handling  of  products  on  the  streets  and  car  lines,  but 
with  respect  to  lighting  and  drainage.  As  R.  B.  Woodworth 


46  ORE  MINING  METHODS 

expresses  it,  "  A  mine  is  nothing  less  than  an  industrial 
plant  underground." 

Maintenance  of  Output.  —  Irrespective  of  the  method  of 
development  employed  in  opening  a  mineral  deposit  a  very 
important  consideration  is  how  large  outputs  can  be  ob- 
tained and  maintained,  assuming  that  the  deposit  is  of 
sufficient  size  to  warrant  large-scale  operations.  The 
output  from  a  given  opening  depends  upon  a  number  of 
factors,  such  as  depth  of  shaft  or  length  of  incline  and 
consequently  the  number  of  levels  or  floors  that  can  be 
worked,  number  of  hoisting  or  hauling  compartments, 
capacity  of  hoist,  and  method  of  handling  ore  underground. 

While  the  capacity  of  a  mine  may  be  increased  by  adding 
to  the  nunber  of  compartments  in  the  main  shaft  or  haul- 
age way  yet  there  is  a  limit  to  the  number  of  compartments 
that  can  be  efficiently  operated.  Further  increase  in  output 
can  be  obtained  only  by  providing  additional  shafts  or  other 
openings.  A  mine  can,  therefore,  be  considered  as  made  up 
of  a  number  of  units,  the  unit  being  a  separate  opening. 

If  more  than  one  opening  is  employed  the  question  as  to 
number  of  openings  and  distance  between  them  must  be 
definitely  answered.  The  number  of  openings  required 
can  be  obtained  directly  from  the  output  desired  and  the 
capacity  of  each  unit.  The  distance  between  openings 
depends  largely  upon  the  method  of  handling  ore  under- 
ground and  consequently  upon  whether  ore  reserves  are 
maintained  or  ore  pockets  are  employed. 

The  limiting  distances  for  efficient  work  in  moving  loaded 
cars  by  hand  are  between  600  and  800  ft.;  therefore,  the 


DEVELOPMENT  OF  MINES  47 

effective  width  of  workings  served  by  a  unit  is  1200  to  1600 
ft.,  considering  the  length  of  levels  on  both  sides  of  the 
shaft  or  incline.  With  mule  or  mechanical  haulage  and  well- 
kept  tracks  the  limits  can  be  materially  increased. 

The  nature  of  levels  is  largely  exploratory,  consequently 
the  knowledge  gained  in  the  early  work  of  opening  a  mine, 
permits  the  lower  levels  to  be  placed  further  apart.  Greater 
distances  are  also  permissible  with  orebodies  of  large  size 
and  uniform  in  content.  Owing  to  the  expense  of  forming 
and  maintaining  track  for  handling  ore  on  each  level, 
tramming  levels  may  be  placed  considerable  distances 
apart  and  the  ore  ^delivered  to  them  by  ore-chutes  and 
slides. 

The  number  of  levels  or  floors  is  an  important  considera- 
tion and  great  care  must  be  taken  in  the  development  work 
in  order  that  the  supply  of  ore  coming  from  the  various 
stopes  may  be  maintained.  This  can  be  accomplished  by 
forming  ore  reserves  of  either  blocked-out  or  broken  ore, 
which  are  maintained  by  opening  up  new  levels  below  as 
those  above  are  exhausetd.  In  many  mines  it  is  the  prac- 
tice to  open  up  a  new  level  each  month,  and  yet  in  spite  of 
such  systematic  development  the  occurrence  of  barren 
ground,  low-grade  ore,  or  the  presence  of  faults,  may  ne- 
cessitate radical  changes  in  plans  to  maintain  the  ore  supply. 
Exploration  by  diamond  drill  is  an  important  adjunct  to 
the  work  of  establishing  and  maintaining  ore  reserves,  the 
expense  of  which  is  thoroughly  justified. 

Careful  and  well-planned  development  systems  are  neces- 
sary for  the  proper  working  of  mineral  deposits  and  while 


48  ORE  MINING  METHODS 

the  expense  may  be  considerable  the  saving  in  operating 
cost  and  the  high  percentage  extraction  of  ore  are  sufficient 
warrant  for  the  extra  expenditure  and  time  involved. 

BIBLIOGRAPHY   OF   DEVELOPMENT   OF   MINES 
GENERAL 

Vertical  vs.  Inclined  Shafts,  by  John  M.  Nichol.     The  Engineering  Maga- 
zine, Aug.  1912,  p.  764. 
Method  of  Development  of  the  Morro  Velho,  the  Deepest  Mine  in  the  World. 

Mining  and  Scientific  Press,  vol.  107,  p.  380. 
Development  of  a  Complex  Branching  Vein  by  Inclined  Shaft.    Mining  and 

Scientific  Press,  vol.  1 06,  p.  936. 
Foot  Wall  Shafts  in  Lake  Superior  Copper  Mines,  by  L.  L.  Hubbard. 

Trans.  Lake  Superior  Mining  Inst.,  vol.  17,  p.  144. 
Ore  Breaking  at  Lake  Superior,  by  W.  R.  Crane.    Eng.  and  Mining  Jour., 

vol.  82,  p.  767. 

The  Interval  Between  Levels.     Eng.  and  Mining  Jour.,  vol.  85,  p.  454. 
Caving  System  in  Chisholm  District,  by  L.  D.  Davenport.     Eng.  and 

Mining  Jour.,  vol.  94,  p.  437. 
Iron  Mining  in  the  Birmingham  District,  Alabama,  by  W.  R.  Crane.     Eng. 

and  Mining  Jour.,  vol.  79,  p.  274. 
The   Cresson  Mine,   by  R.  L.  Herrick.      Mines   and  Minerals,  vol.  31, 

P-  735- 
Mining  Methods  in  the  North,  by  T.  A.  Rickard.     Mining  and  Scientific 

Press,  vol.  98,  p.  382. 
Transvaal  Gold  Mining  —  Present  and  Future  Methods,  by  F.  H.  Hatch. 

Eng.  Magazine,  vol.  43,  p.  505. 
Davis  Pyrite  Mine,  Massachusetts,  by  J.  J.  Rutledgs.     Eng.  and  Mining 

Jour.,  vol.  82,  p.  673. 
The  Diamond  Mines  of  South  Africa,  by  G.  F.  Williams.     Trans.  Am.  Inst. 

Mining  Engrs.,  vol.  15,  p.  392. 
The  Clinton  Iron-Ore  Deposits  in  Alabama,  by  Ernest  F.  Burchard.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  40,  p.  75. 
Gold  Mining  and  Milling  in  Western  Australia,  by  A.  G.  Charleton,  pp* 

508-568. 
Lake  Superior  Copper  Mining:     Present  and  Future,  by  T.  T.  Read. 

Mining  and  Scientific  Press,  vol.  no,  p.  209. 
Mining  Copper  at  Lake  Superior,  by  Claude  T.  Rice.    Eng.  and  Mining 

Jour.,  vol.  94,  p.  267. 


DEVELOPMENT  OF  MINES  49 

Drifting  and  Stoping  at  Lake  Superior,  by  W.  R.  Crane.  Eng.  and  Mining 
Jour.,  vol.  82,  p.  645. 

Development  at  the  Esperanza  Mine,  El  Oro,  Mexico,  by  W.  E.  Hindry. 
Mining  and  Scientific  Press,  vol.  99,  p.  822. 

Mine  Openings.     The  Business  of  Mining,  by  Arthur  J.  Hoskin,  p.  93. 

Method  of  Mining  Iron  Ore  at  Sunrise,  Wyoming,  by  B.  W.  Vallat.  Engi- 
neering and  Mining  Jour.,  vol.  85,  p.  399. 

DEVELOPMENT   OF  SUB-LEVEL  AND   SUB-DRIFT  METHODS 

Methods  of  Iron  Mining  in  Northern  Minnesota,  by  F.  W.  Denton.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  27,  p.  344. 
Mining  Methods  at  Kimberly,  by  John  T.  Fuller.     Eng.  and  Mining  Jour., 

vol.  94,  p.  887. 

The  Miami-Inspiration  Ore-Zone,  by  C.  F.  Tolman,  Jr.,  Mining  and  Scien- 
tific Press,  vol.  99,  p.  646. 
Montreal  Iron  Mine,  Gogebic  Range,  by  Geo.  E.  Des  Rochers.     Eng.  and 

Mining  Jour.,  vol.  95,  p.  955. 
Caving  System  at  Ohio  Copper  Mine,  by  Clarence  G.  Bamberger.     Eng. 

and  Mining  Jour.,  vol.  93,  p.  701. 

Diamond  Mining,  by  Wm.  Taylor.     Mines  and  Minerals,  vol.  28,  p.  267. 
Mining  Methods  at  the  Magpie  Iron  Mine,  by  A.  Hasselbring.     Bull. 

No.  59,  Canadian  Mining  Inst.,  Mar.  1917,  p.  261. 

Cananea  Caving  and  Slicing  Systems,  by  R.  L.  Herrick.     Mines  and  Min- 
erals, vol.  30,  p.  23. 
Mining  Methods  Employed  at  Cananea,  Mexico,  by  M.  J.  Elsing.     Eng. 

and  Mining  Jour.,  vol.  90,  p.  914. 
The  Mitchell  Slicing  System  at  Bisbee,  Arizona,  by  M.  J.  Elsin^.     Eng. 

and  Mining  Jour.,  vol.  90,  p.  174. 
Iron  Mining  on  the  Mesabi  Range,  by  A.  L.  Gerry.     Eng.  and  Mining  Jour., 

vol.  94,  p.  693. 
Los  Pilares  Mine,  by  Edward  M.  Robb,  Jr.     Mines  and  Minerals,  vol.  31, 

p.  106. 
Mines  and  Mill  of  the  Consolidated  Mercur  Company,  by  Roy  Hutchins 

Allen.     Eng.  and  Mining  Jour.,  vol.  89,  p.  1273. 
The  Caving  System  at  the  Darien  Mine,  by  A.  B.  Chase.     Mining  and 

Scientific  Press,  vol.  95,  p.  238. 
Notes  on  Caving  System  in  Northern  Iron  Mines,  by  Albert  H.  Fay.    Eng. 

and  Mining  Jour.,  vol.  88,  p.  961. 
Marquette-Range  Caving  Method,  by  H.  H.  Stoek.     Mines  and  Minerals, 

vol.  30,  p.  193. 
Caving  System  in  Chisholm  District,  by  L.  D.  Davenport.     Eng.  and 

Mining  Jour.,  vol.  94,  p.  437. 


50  ORE  MINING  METHODS 

Copper  Deposits  of  Globe-Kelvin  District,  by  Edwin  Higgins.     Eng.  and 

Mining  Jour.,  vol.  89,  p.  813. 
The  Miami  Copper  Mine,  Arizona,  by  R.  L.  Herrick.     Mines  and  Minerals, 

vol.  30,  p.  80. 
Mining  the  Treadwell  Lode,  by  T.  A.  Rickard.     Mining  and  Scientific 

Press,  vol.  97,  p.  85. 
Mining  on  the  Gogebic  Range,  by  P.  S.  Williams.     Mines  and  Minerals, 

vol.  31,  p.  712. 
Mining  Methods  in  the  Waihi  Mine,  by  Jas.  L.  Gilmour  and  W.  H.  Johnston. 

Mining  and  Scientific  Press,  Dec.  21,  1912,  p.  789. 
Notes  on  the  Gold-Mines  of  Zaruma,  Ecuador,  by  J.  Ralph  Finlay.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  30,  p.  248. 
Mining  the  Prince   Consolidated  Ores,  by  D.  W.  Jessup.     Mining  and 

Scientific  Press,  vol.  106,  p.  820. 
Low  Cost  of  Mining  on  the  Mother  Lode,  by  William  G.  Devereux.     Eng. 

and  Mining  Jour.,  vol.  92,  p.  546. 


CHAPTER  III 
METHODS    OF    STOPING 


THE  openings  in  metal  mines  from  which  ore  is  taken  are 
called  stopes  and  the  methods  employed  in  breaking  down 
the  ore  are  known  as  stoping.  Stoping  then  constitutes 
the  fundamental  operation  in  the  extraction  of  ore  and  must 
be  well  understood  before  a  discussion  of  methods  of  mining 
is  undertaken.  Under  certain  conditions  the  methods  of 
stoping  constitute  in  themselves  methods  of  mining  and 
give  the  latter  the  name  of  the  kind  of  stoping  employed. 

The  methods  of  stoping  employed  in  the  mines  of  the 
United  States  and,  in  fact,  throughout  the  mining  world  may 
be  outlined  as  follows: 

1.  Overhand  Stoping. 

2.  Underhand  Stoping. 

3.  Breast  Stoping. 

4.  Resuing. 

Other  methods  of  stoping  may  result  through  combining 
overhand  and  underhand  stoping,  such  as: 

1.  Combined  or  overhand-underhand  stoping. 

2.  Side  stoping,  sometimes  called  breast  stoping. 

3.  Longwall  stoping  or  cutting-out  stoping. 


52  ORE  MINING  METHODS 

The  direction  of  the  working  face  with  respect  to  the 
lines  of  development,  as  levels,  raises  and  winzes,  furnishes 
the  basis  for  the  above  classification.  The  methods  of 
stoping  as  outlined  may  then  be  defined  as  follows:  Over- 
hand stoping  is  working  up  the  dip  and  usually  in  a  direc- 
tion diagonal  to  raises  and  winzes;  underhand  stoping  is 
working  down  the  dip  also  in  a  direction  diagonal  to  raises 
and  winzes;  breast  stoping  may  be  either  overhand  or  under- 
hand stoping  applied  to  deposits  of  slight  inclination  and 
resembles  breast  work  in  coal  mining;  combined  stoping  is 
where  both  overhand  and  underhand  stoping  are  carried  on 
in  the  same  working  place  or  stope,  the  two  lines  of  working 
faces  extending  diagonally  up  and  down  the  stope  from  a 
common  point  above  or  below  the  center  of  the  stope;  side 
stoping  is  where  the  working  face  is  parallel  with  the  winzes; 
while  longwall  stoping  has  the  working  face  parallel  with  the 
levels.  These  terms  are,  however,  more  or  less  elastic  and 
may  be  employed  differently  in  various  districts  and  mines. 

The  conditions  influencing  and  controlling  the  choice  of 
method  of  stoping  are  as  follows : 

1.  Character  of  ore  and  its  value. 

2.  Occurrence  of  valuable  mineral. 

3.  Width  of  vein  or  deposit. 

4.  Dip  and  pitch  of  orebody. 

5.  Size  and  shape  of  orebodies  other  than  in  veins. 

6.  Character  and  condition  of  wall  rocks. 

7.  Cost  of  timber  for  support. 

Of  the  conditions  given  above  that  of  dip  or  inclination 
probably  exerts  the  greatest  influence  on  method  of  stoping, 


METHODS  OF  STOPING  53 

being  the  principal  factor  in  the  choice  between  overhand 
and  underhand  methods.  Wide  veins  or  large  deposits 
while  often  worked  by  overhand  stoping  may  require 
breast  stoping  wholly  or  in  part.  The  character  and 
occurrence  of  the  valuable  mineral  while  not  necessarily 
influencing  the  method  of  attack  may  require  modifications 
which  are  more  or  less  radical.  The  character  of  wall  rock 
concerns  the  method  of  support  mainly  and  therefore  affects 
the  general  scheme  of  working  rather  than  the  method  of 
attack  or  method  of  stoping. 

The  handling  of  mineral  in  stopes  varies  widely  with  the 
method  of  stoping  employed,  and  may  even  necessitate  a 
change  in  method  in  order  that  the  work  may  be  facilitated 
and  cheapened.  The  factors  which  influence  the  handling  of 
mineral  in  stopes  are,  in  order  of  importance,  dip  and  width 
of  vein  and  character  and  occurrence  of  mineral. 

Overhand  Stoping.  —  This  method  of  stoping  is  probably 
more  extensively  employed  than  the  other  methods,  being 
used  in  practically  all  kinds  of  metal  mines  where  condi- 
tions are  at  all  suitable.  Overhand  stoping  is  commonly 
employed  in  both  narrow  and  wide  veins,  in  moderately 
highly  or  highly  inclined  stratified  deposits,  and  in  massive 
deposits. 

The  location  of  a  body  of  ore  having  been  determined 
by  levels  and  raises  or  winzes  driven  through  it,  the  work 
of  cutting  out  the  ore  is  begun  by  attacking  it  on  one  or 
both  sides  of  a  raise  or  winze,  which  connects  the  two  levels 
and  extends  through  the  ore  located  at  that  point.  (See 
Figs.  12  and  13.) 


54  ORE  MINING   METHODS 

As  there  are  several  methods  of  procedure  that  are  de- 
pendent upon  the  character  and  occurrence  of  the  mineral 
in  the  vein,  the  determining  conditions  should  now  be  stated. 
Where  all  of  the  vein  matter  is  sufficiently  valuable  to  mine 


FIG.  i2. —  Overhand  Sloping,  'Breaking-Through.' 

it  may  be  broken  down,  transferred  to  the  level  below,  loaded 
into  cars  and  hauled  away.  There  are  cases,  however, 
where  it  is  not  possible  or  advisable  to  dispose  of  the  ore  as 
rapidly  as  it  is  mined,  although  its  preparation  for  with- 
drawal from  the  stopes  is  an  important  consideration.  As 
ore  when  broken  increases  in  bulk  about  40  per  cent  it  is 
evident  that  to  provide  working  space  for  the  miners  at  the 


METHODS  OF  STOPING  55 

face  a  certain  amount  of  the  broken  ore  will  have  to  be  drawn 
off  after  a  certain  advance  has  been  made.  This  is  known 
as  '  shrinkage '  stoping,  while  the  ore  remaining  in  the  stope 
is  called  an  'ore  reserve'  and  serves  a  useful  purpose  in 
regulating  the  output  of  the  mine.  On  the  other  hand  the 
bulk  of  the  vein  matter  may  be  barren  or  so  low-grade  as 
to  warrant  only  the  least  possible  handling,  in  which  case 
provision  must  be  made  for  both  the  storage  of  the  waste 
and  the  disposal  of  the  valuable  mineral. 

In  either  of  the  cases  mentioned  some  provision  must  be 
made  for  the  support  of  the  ore  or  waste  left  in  the  stopes,  if 
that  is  done.  If  all  of  the  ore  is  removed  from  the  stopes  as 
rapidly  as  it  is  broken  down,  then  supports  for  the  main- 
tenance of  walls  and  protection  of  levels  is  all  that  is  neces- 
sary. Stope  marked  A-i,  in  Fig.  13,  illustrates  the  first 
case  mentioned,  where  the  ore  is  drawn  off  as  soon  as  broken 
down.  Stopes  B  and  B-i  may  be  taken  as  representing 
the  condition  where  ore  is  stored  in  the  stopes,  forming  an 
ore  reserve.  Stope  A  may  represent  the  condition  existing 
in  a  precious-metal  mine  where  the  gold  or  silver  occurs  in 
small  veins  or  stringers,  the  bulk  of  the  vein-filling  being 
barren  or  low-grade  and  is  left  in  the  stope. 

Stopes  may  be  opened  in  two  ways,  namely,  by  beginning 
at  a  winze  or  raise,  or  by  first  driving  a  'raise  stope.'  Raise 
stoping  differs  from  driving  raises  mainly  in  width  of  passage 
or  cut  made,  the  usual  width  for  a  raise  stope  varying  from 
20  to  25  feet.  From  such  a  starting  point  the  height  of  the 
drift  may  be  increased  by  a  'cutting-out'  stope,  and  con- 
sists in  removing  the  vein-content  in  a  more  or  less  regular 


ORE  MINING  METHODS 


a 

c 
U 


o 

bJO 


METHODS  OF  STOPING  57 

way,  i.e.,  by  cutting  out  a  portion  of  definite  width  from  the 
back  of  the  level.  This  is  the  usual  method  of  procedure 
when  a  stope  is  started  after  the  level  has  been  run.  When, 
however,  drifting  precedes  breaking  ore  or  stoping  by  but 
a  few  feet,  '  drift  stoping '  is  employed  in  enlarging  the  level 
previous  to  the  actual  work  of  stoping,  or  cutting-out  stoping. 
Drifting  and  stoping  are  then  combined  in  one  operation 


FIG.  14. — Use  of  Stulls  and  Waste-Filling. 

and  consist  in  carrying  a  face  about  25  ft.  high  practically 
the  full  width  of  the  vein. 

As  each  cutting-out  stope  is  advanced,  receding  from  the 
common  starting  point,  and  is  followed  by  others  at  regular 
intervals,  the  working  face  of  the  stope  assumes  an  inverted- 
stepped  appearance  as  shown  in  stopes  B  and  B-i,  Fig.  13. 
The  successive  stope  faces  are  then  called  'back-s topes/ 
being  numbered  in  order  from  the  drift-stope  upward 
(B,  Fig.  13).  The  parts  of  the  stope  designated  as  'toe' 
and  'heel'  are  shown  in  B-i. 


58  ORE  MINING  METHODS 

The  usual  practice  in  the  mines  of  the  United  States  is  to 
carry  the  stopes  up  from  the  levels  without  leaving  a  row 
of  pillars  directly  above  them  as  shown  in  stope  B-i.  Wall 
pillars  are,  however,  commonly  left  for  support  (see  stope 
A-i),  which  is  the  usual  practice  in  veins  of  moderate 
inclinations.  In  more  highly  inclined  veins,  unless  of  too 
great  width,  stulls  and  lagging  with  ore  or  waste-filling  are 
employed.  (See  stopes  A  and  B,  Fig.  13  and  Fig.  14.) 

Overhand  stoping  is  employed  in  veins  varying  in  dip 
from  a  few  degrees  up  to  the  vertical,  but  may  be  used  more 
readily  in  veins  of  slighter  inclination  than  underhand 
stoping. 

Underhand  Stoping.  —  In  many  respects  underhand  re- 
sembles overhand  stoping,  and  may  be  said  to  be  overhand 
stoping  upside  down,  i.e.,  the  work  of  breaking  the  ore  is 
downward  instead  of  upward.  (See  stopes  C  and  B, 
Fig.  13.)  The  relation  between  the  stoping  face  and  the 
lines  of  development  is  also  similar  to  that  in  overhand 
work. 

The  Cornish  system  of  underhand  stoping  consists  in 
sinking  a  pit  in  the  floor  of  a  level  and  then  beginning  the 
work  of  removing  the  ore  by  working  laterally  therefrom. 
This  method  has  two  serious  disadvantages,  namely:  all 
the  ore  has  to  be  shoveled  out  or  raised  by  windlass,  and  the 
accumulation  of  water  in  the  pit  so  formed  will,  if  the  mine 
is  wet,  necessitate  pumping.  Where  a  piece  of  ground  of 
limited  extent  is  known  to  contain  valuable  ore  the  Cornish 
system  of  stoping  may  be  not  only  advisable  but  necessary. 
When,  however,  ore  has  been  blocked  out  between  levels 


METHODS  OF  STOPING  59 

and  known  to  extend  for  some  distance  along  the  stope,  the 
method  employed  in  removing  the  ore  should  be  undertaken 
on  a  larger  scale  and  more  systematically.  Provision  will 
have  to  be  made  also  for  handling  the  ore  quickly  and  cheaply 
and  for  keeping  the  workings  free  from  water.  This  can 
readily  be  accomplished  by  beginning  stoping  on  the  sides 
of  a  raise  or  winze  connecting  levels.  Ore  and  water  are 
both  discharged  through  the  connecting  passage  to  the  lower 
level,  the  former  being  loaded  into  cars  while  the  latter  is 
conducted  by  drains  to  the  sumps  located  in  the  levels  or 
at  the  foot  of  the  shaft.  (See  left-hand  portion  of  stope  C.) 

Underhand  stoping  unlike  overhand  work  is  not  applicable 
to  deposits  where  only  a  small  portion  of  the  vein-content 
is  valuable,  for  the  very  evident  reason  that  there  is  no  con- 
venient place  to  store  the  waste.  Occasionally  a  line  of 
stulls  may  be  set  in  the  stope,  with  a  flooring  of  lagging, 
thus  forming  a  staging  upon  which  a  limited  quantity  of 
waste  may  be  thrown.  The  method  is,  however,  applicable 
to  both  high-  and  low-grade  deposits  the  whole  or  a  large 
part  of  which  is  workable,  also  to  massive  deposits  where 
the  work  of  stoping  is  carried  on  in  horizontal  floors. 

Underhand  stoping  may  be  employed  on  quite  a  range  of 
dips,  but  is  most  successful  in  veins  of  50°  and  up,  due  to  the 
necessity  of  handling  ore  by  gravity.  (See  Fig.  15.) 

Underhand  stoping  may  be  done  in  very  small  veins  even 
as  narrow  as  18  inches. 

Both  overhand  and  underhand  stoping  may  begin  next  to 
the  shaft,  the  width  of  shaft  pillars,  if  employed,  determining 
the  beginning  of  the  stopes.  A  winze  or  raise  is  driven 


6o 


ORE  MINING  METHODS 


connecting  the  levels,  forming  the  shaft  pillars  and  at  the 
same  time  providing  a  point  of  attack  in  s toping.  In  over- 
hand work  the  stope  is  begun  on  the  corner  where  the  winze 
and  level  intersect,  successive  cuts  increasing  both  the  width 
and  height  of  the  stope.  With  underhand  stoping,  unless 
no  arch  pillars  are  left,  the  work  of  removing  the  ore  can- 
not begin  until  a  drift  is  run  below  the  arch  pillars,  thus 


FIG.  15.  —  Underhand  Stoping  Methods  Showing  Wall  Pillars  and  Waste- Stulls. 

definitely  determining  their  position  and  forming  them.  At 
the  intersection  of  the  drift  and  winze  or  raise  the  work  of 
stoping  may  begin  and  extend  downward  until  the  level 
below  is  reached.  The  beginning  of  stoping  next  to  the 
shaft  is  shown  in  stopes  B  and  B-i  for  overhand  stoping 
and  in  stopes  C  and  C-i  for  underhand  work. 

Underhand  stoping  is  largely  employed  in  massive  de- 
posits and  in  slightly  inclined  bedded  deposits  of  consider- 
able thickness.  The  opening  of  a  stope  may  be  accom- 


METHODS  OF  STOPING 


61 


62 


ORE   MINING  METHODS 


plished  by  sinking  a  shaft  to  or  near  the  deposit  and  drifting 
into  the  orebody  at  a  point  as  near  the  top  as  possible- 
The  stope  may  be  increased  in  height  by  cutting  out  the 
floor  of  the  drift,  work  beginning  at  the  shaft  and  extending 
to  the  orebody  where  benches  are  formed  by  successively 
lifting  the  floor  of  the  drift.  The  usual  height  of  the  indi- 
vidual benches  is  8  to  10  ft.,  but  a  number  may  be  run 
together  forming  a  single  bench  of  50  to  60  ft.  in  height. 


FIG.  17.  —  Underhand  Sloping  in  'Sheet-Ground/  Joplin  District 
Similar  to  Those  in  Massive  Deposits. 


Conditions 


A  plan  of  a  mine  workings  in  which  underhand  s toping 
has  been  employed  is  shown  in  Fig.  16,  the  shaded  portions 
indicating  parts  of  the  floor  that  have  been  stoped  to  a 
lower  level  than  the  workings  in  main  body  of  the  deposit. 
The  more  or  less  regular  arrangement  of  pillars  for  support 
of  workings  is  also  shown.  (See  also  Fig.  17.) 

As  the  shape  and  slope  of  the  face  of  the  stope  in  such 
deposits  are  entirely  under  the  control  of  the  miner  and  not 


METHODS  OF  STOPING  63 

dependent  upon  the  dip  of  the  vein,  the  passing  of  the  ore 
to  the  foot  of  the  stope  can  be  readily  accomplished,  its 
transference  to  the  shaft  being  done  in  cars. 

Combined  Sloping.  —  Occasionally  a  stope  will  be  worked 
by  both  overhand  and  underhand  stoping,  overhand  being 
employed  at  the  bottom  and  underhand  at  the  top  of  the 
stope.  The  dip  of  the  vein  determines  the  proportionate 
length  of  the  two  working  faces;  with  certain  dips  as 
50  to  55°  the  length  of  the  underhand  stoping  face  exceeds 
that  of  the  overhand  face,  while  with  dips  of  25  to  30°  the 
reverse  is  true.  The  reason  why  underhand  stoping  is 
employed  at  the  top  and  overhand  at  the  bottom  of  the 
stope  is  that  with  a  reversal  of  the  arrangement  a  reentrant 
angle  would  be  formed  between  the  two  working  faces,  thus 
forming  a  ' tight  corner'  which  is  difficult  to  work.  An 
advantage  of  the  usual  arrangement  is  that  the  angle  formed 
by  the  faces,  coming  as  it  does  in  the  center  of  the  stope, 
makes  the  forming  of  wall  pillars  comparatively  easy;  the 
more  acute  the  angle  the  more  readily  are  the  pillars  formed. 

With  high  dips  the  underhand  face  increasing  in  length 
has  all  the  advantages  of  underhand  stoping  and  at  the 
same  time  materially  assists  in  handling  waste  and  placing 
it  on  '  stull  floors '  in  the  overhand  part  of  the  stope.  When 
the  dip  is  such  as  to  require  that  the  overhand  face  be  longer, 
the  short  underhand  stope  above  may  be  of  advantage  in 
handling  a  considerable  part  of  the  ore  at  the  top  of  the 
stope,  which  can  be  thrown  or  raised  to  the  level  above 
instead  of  being  transferred  down  through  the  stope  to  the 
level  below.  Higher  stopes  can  be  worked  to  advantage 


64  ORE  MINING  METHODS 

by  combining  overhand  and  underhand  stoping,  which  per- 
mits the  levels  to  be  placed  farther  apart  and  so  reduces 
the  cost  of  development  work.  The  chief  advantages  of  the 
method  then  lie  in  the  convenience  of  handling  ore  and 


FIG.  1 8.  —  Combined  Stoping  in  Moderately  Dipping  Vein. 

waste  in  the  stopes   and  in  reducing   development  work. 
(See  Fig.  18.) 

Breast  Stoping.  —  When  the  inclination  of  the  vein  or  bed 
is  such  that  the  broken  ore  cannot  be  passed  to  the  level 
below  by  gravity,  but  remains  close  to  the  face  and  must 
be  loaded  into  cars  at  that  point,  neither  overhaad  nor 
underhand  stoping  can  be  employed  to  advantage.  The 
method  employed  is  then  ordinary  breast  work,  and  the  di- 
rection of  the  face  may  be  carried  in  practically  any  direction. 
This  method  permits  the  placing  of  holes  so  as  best  to 
take  advantage  of  the  conditions  existing  at  the  face;  the 


METHODS  OF  STOPING  65 

principal  disadvantage  being  that  the  cars  must  be  run  to 
the  face,  thus  increasing  the  cost  of  handling. 

Side  Stoping.  —  As  previously  pointed  out,  side  stoping  and 
breast  stoping  are  often  spoken  of  as  being  similar  opera- 
tions, but  strictly  speaking  they  are  not.  Side  stoping  is 
carried  parallel  with  winzes  or  raises,  which  as  in  the  case  of 
the  other  methods  of  stoping  are  the  initial  points  of  attack. 
This  method  of  stoping  is  not  confined  to  slight  inclinations 
as  would  be  the  case  were  it  similar  to  breast  stoping. 

There  is  no  method  of  stoping  in  which  the  direction  of 
the  working  face,  the  distinguishing  characteristic  of  the 
methods,  is  more  than  approximately  maintained,  and  there 
is  no  method  of  stoping  which  is  apt  to  have  the  direction  of 
the  face  vary  more  than  side  stoping.  Raise  stoping  and 
side  stoping  are  similar  if  parallelism  to  raises  and  winzes 
is  the  distinction,  but  raise  as  well  as  drift  and  cutting-out 
stoping  are  phases  of  overhand  stoping;  however,  as  the 
term  side  stoping  has  been  applied  to  a  certain  direction  of 
working  in  stoping,  and  as  it  is  similar  to  raise  stoping,  the 
name  may  be  applied  to  both  alike.  (See  stope  A,  left- 
hand  side,  Fig.  13.)  The  first  cut  in  side  stoping  is  driven 
directly  up  the  dip,  being  commonly  employed  in  forming 
shaft  pillars,  dead-ends,  etc.,  and  in  starting  cutting-out 
stopes  in  overhand  work.  When  employed  in  this  manner 
side  stoping  serves  as  a  supplementary  method  to  overhand 
stoping,  but  its  application  may  be  extended  to  the  regular 
work  of  breaking  ore,  successive  cuts  being  taken  off  the 
sides  of  the  first  side  or  raise  stope.  The  tendency  is, 
however,  for  the  direction  of  the  work  to  change  so  radically 


66  ORE  MINING  METHODS 

as  to  lose  its  identity  as  side  stoping  and  merge  into  over- 
hand work  or  underhand  work,  usually  the  former. 

Longwall  Stoping.  —  Raise  stoping  has  been  shown  to  be 
a  phase  of  overhand  stoping.  In  a  similar  manner  cutting- 
out  stoping  corresponds  to  longwall  work.  Further,  breast 
and  side  stoping  may  be  said  to  be  similar  to  longwall  work 
unless  parallelism  with  the  longer  dimension  of  the  stope  is 
a  desideratum. 

As  usually  carried  on,  longwall  stoping  is  applied  to  that 
class  of  overhand  work  where  the  working  face  is  parallel 
with  the  levels  and  constitutes  an  important  part  of  the 
work  of  breaking  ore  as  the  work  of  stoping  is  carried  on  in 
many  districts.  (See  stope  A,  Fig.  13.)  While  longwall 
stoping  may  be  employed  in  veins  of  slight  or  moderate 
inclination,  as  when  breast  stoping  is  applicable,  and  cars 
are  run  parallel  with  the  face,  yet  it  is  just  as  often  employed 
in  steeply  inclined  veins  where  ore  or  waste  is  stored  in  the 
stopes.  (See  stope  A,  Fig.  13.)  Although  there  may  be 
no  advantage  in  breaking  ore  by  this  method,  yet  there  is  a 
positive  advantage  in  handling  ore  on  a  level  floor,  compared 
with  similar  work  on  an  irregular  and  sloping  bank  of  ore 
as  in  overhand  stoping.  (Compare  stopes  A  with  B  and 
B-i,  Fig.  13.) 

Resuing.  -  -  This  method  is  a  special  application  of  stop- 
ing to  narrow  veins  or  stringers  and  is  in  reality  a  stripping 
method.  Resuing  consists  in  opening  up  the  stopes  not  in 
the  vein  but  in  the  wall  rock,  by  whatever  method  of  stoping 
seems  best  adapted  to  the  existing  conditions,  and  when 
sufficient  space  has  been  provided  by  stripping  one  wall 


METHODS  OF  STOPING  67 

from  the  ore  it  is  broken  down  and  handled  practically 
independently  of  the  waste. 

When  the  values  are  definitely  known  to  occur  in  the  vein 
alone,  this  method  of  procedure  is  especially  applicable,  but 
when,  as  often  happens,  the  values  also  extend  into  the  walls, 
the  usual  methods  of  stoping  are  probably  more  applicable.1 
The  extra  width  of  drifts  and  stopes  may  also  serve  to  un- 
cover and  discover  other  workable  portions.  Where  the 
condition  of  the  vein-filling  and  wall  rock  permit,  much 
cleaner  ore  can  be  produced,  which  may  be  the  determining 
factor  in  the  economical  working  of  a  given  deposit.  How- 
ever, the  sorting  of  waste  rock  under  the  unfavorable  con- 
ditions existing  underground,  often  resulting  in  the  necessity 
of  sending  considerable  waste  rock  to  the  surface  and  the 
treatment  of  the  same,  may  make  it  inadvisable  to  employ 
resuing. 

Resume  of  Stoping.  —  The  conditions  under  which  the  dif- 
ferent methods  of  stoping  are  especially  applicable,  with  the 
advantages  and  disadvantages  of  their  use,  are  as  follows: 

Overhand  Stoping  has  a  wide  range  of  application  both 
as  to  character,  inclination  and  width  of  deposit.  The 
method  is  employed  in  very  narrow  and  very  wide  veins 
and  even  massive  deposits,  but  when  considered  as  a 
distinct  method  of  mining  its  application  is  limited  to 
moderately  narrow  veins  or  beds,  as  from  4  to  12  ft.,  and 
to  inclinations  of  10  to  90°  with  the  horizontal. 

1  "A  peculiarity  of  the  Porcupine  goldfield  is  the  way  in  which  the  metal 
is  'shot'  through  the  schist  on  either  side  of  the  veins.  This  is  so  to  such 
an  extent  that  in  some  of  the  mines  a  vein  of  two  inches  of  quartz  is  mined 
to  a  width  of  five  or  six  ft. " 


68  ORE  MINING  METHODS 

The  advantages  of  overhand  stoping  are: 

1.  Levels  may  be  driven  at  considerable  distance  apart, 
ranging  from  100  to  150  ft.,  and  occasionally  greater  dis- 
tances. 

2.  Greater  safety  to  men,  as  the  roof  is  accessible  and  can 
be  examined  and  made  safe  as  signs  of  weakness  develop. 
This  is  especially  true  when  the  roof  is  the  working  face, 
as  is  the  case  with  steeply  inclined  deposits. 

3.  A  large  working  force  can  be  employed  in  a  compara- 
tively small  space,  which  results  in  reduced  cost  of  extraction 
per  ton  of  ore. 

4.  Either  ore  or  waste  can  be  stored  in  the  stopes,  which 
assists  materially  in  the  support  of  the  workings. 

5.  The  ore  as  broken  down  falls  free  of  the  face  and  by 
gravity  moves  toward  the  point  of  delivery. 

6.  Where  ore  is  stored  in  the  stopes  a  'reserve'  is  formed, 
thus  regulating  and  maintaining  the  output  independent 
of  temporary  stoppage  of  mining  operations. 

7.  Large  and  regular  outputs  are  possible. 

8.  The  face  of  the  stope  is  usually  opposite  a  number  of 
chutes  into  which  the  ore  may  be  thrown. 

The  disadvantages  of  overhand  stoping  are: 

1.  Considerable  timber  is  required  for  support,  or  if  wall 
pillars  are  employed  a  loss  of  ore  may  result. 

2.  When  ore  is  left  in  the  stopes  it  serves  as  a  platform 
for  the  men  to  work  upon,  which  may  prevent  a  stope  being 
emptied  until  all  ore  is  removed  up  to  the  arch  pillars. 
This  difficulty  may  be  largely  obviated  by  using  '  stull-floors,' 
but  this  necessitates  the  use  of  considerable  more  timber. 


METHODS  OF  STOPING  69 

3.  Dust  is  troublesome,  especially  in  dry  mines,  as  the 
holes  are  largely  drilled  'dry.'  By  a  slightly  different 
arrangement  of  the  working  face  the  direction  of  the  holes 
may,  however,  be  altered,  changing  them  from  'dry'  to  'wet.' 

Underhand  Sloping  is  also  employed  in  both  veins  and 
massive  deposits,  but  is  applicable  to  higher  inclinations 
(38  to  90°)  in  veins  than  is  overhand  work.  As  a  distinct 
method  of  mining,  and  not  simply  as  a  method  of  attacking 
the  face,  underhand  s toping  is  applied  equally  well  to  narrow 
and  moderately  wide  veins  and  massive  deposits. 

The  advantages  of  underhand  stoping  are: 

1.  Ease  in  drilling  and  blasting,  especially  when  hand 
drilling  is  done. 

2.  Comparatively  small  amount  of  timber  is  used. 

3.  When  proper  slopes  are  maintained  in  the  stopes  the 
ore  can  be  handled  largely  by  gravity. 

4.  Little  trouble  is  experienced  with  dust. 
The  disadvantages  of  underhand  stoping  are: 

1.  The  method   is  limited  to  veins  or  highly  inclined 
bedded  deposits  where  all  or  a  large  part  of  the  deposit  is 
of  sufficient  value  to  mine. 

2.  Levels  are  run  closer  together  in  order  to  reduce  the 
amount  of  exposed  roof  and  consequently  diminish  the  dan- 
ger of  falls. 

3.  The  working  face  is  small,  the  lower  part  of  the  stope 
face  being  largely  covered  with  broken  ore;    the  output  is 
therefore  small. 

4.  Inconvenience  resulting  from  having  no  'ore  reserve/ 
often  necessitating  underground  or  surface  ore  bins  of  suffi- 


70  ORE  MINING  METHODS 

cient  capacity  to  maintain  the  output  of  the  mine  should  it 
be  necessary  to  temporarily  stop  breaking  ore. 

5.  The  difficulty  experienced  in  disposing  of  waste  sorted 
from  the  ore. 

6.  Loss  of  ore  in  pillars. 

Breast  Sloping  is  applicable  to  inclinations  below  the 
angle  of  repose  of  broken  ore,  which  is  about  38°  with  the 
horizontal.  As  a  rule,  however,  breast  stoping  is  usually 
carried  on  at  much  lower  dips  as  under  10°.  Thick  deposits 
may  be  worked  in  benches,  but  this  usually  leads  to  a 
combination  of  breast  and  underhand  work.  A  deposit 
10  ft.  thick  can  readily  be  worked  by  breast  stoping;  the 
height  of  face  increasing  the  fall  and  consequently  the  dis- 
tance that  the  ore  will  travel  from  the  face  on  moderate 
dips. 

The  advantages  of  breast  stoping  are: 

1.  Deposits  of  low  dip  can  readily  be  worked. 

2.  The  best  conditions  for  mounting  drills  and  taking 
advantage  of  working  face  are  obtained. 

3.  Cars  may  be  run  close  to  the  stope  face. 

4.  Considerable  waste  may  be  left  in  stopes  without 
extra  handling. 

5.  Ease  of  entrance  and  exit  to  and  from  the  stopes. 
The  disadvantages  of  breast  stoping  are: 

1.  Levels  are  close  together. 

2.  Much  timber  is  used  for  support. 

3.  Extra  cost  of  laying  track  and  maintaining  proper 
grade  to  working  face. 

4.  Difficulty  in  handling  ore  in  stopes. 


MEtHODS  OF  STOPING  71 

Resuing  is  applicable  to  very  narrow  veins  alone,  i.e., 
under  30  in.  in  width;  its  chief  advantage  being  that  a 
cleaner  grade  of  ore  can  be  mined  than  when  both  vein  and 
walls  are  broken  together;  further,  it  is  often  useful  in  open- 
ing up  unsuspected  bodies  of  ore  existing  in  the  walls,  but 
as  the  work  is  confined  to  one  wall  only  such  application  is 
limited. 

Other  Methods  of  Sloping  such  as  combined,  side  and  long- 
wall  stoping  are  special  applications  of  overhand  and  under- 
hand stoping  and  are  therefore  employed  under  somewhat 
similar  conditions,  especially  as  to  thickness  and  inclination 
of  deposit. 

The  advantages  of  combined  stoping  are: 

1.  Long  stope  backs,  i.e.,  higher  stopes  may  be  employed 
than  with  underhand  stoping  especially. 

2.  Wall  pillars  can  readily  be  formed  at  the  junction 
of  the  overhand  and  underhand  portions  of  the  stope. 

3.  Waste  can  be  stowed  to  advantage  on  lagged  stulls  in 
the  overhand  portion  of  the  stope. 

4.  A  certain  amount  of  ore  can  be  transferred  to  the 
level  above  from  the  underhand  portion  of  the  stope,  thus 
reducing  the  amount  that  must  be  handled  below. 

5.  The  intermediate  dips  between  those  to  which  over- 
hand and  underhand  stoping  are  applicable  can  be  worked 
to  advantage  by  this  method. 

The  disadvantages  of  combined  stoping  are : 

i.   The  limitations  as  to  dip  vary  probably  between  35 

and  50°,  above  and  below  which  the  method  merges  into 

all  overhand  or  underhand  work. 


72  ORE  MINING  METHODS 

2.  Tight  corners  are  formed  both  at  the  top  and  bottom 
of  the  stope,  when  lines  of  pillars  are  left  for  the  protection 
of  the  miners  in  the  stopes  and  above  the  levels. 

Side  Sloping  is  not  very  extensively  employed,  having 
special  application  in  cutting  out  and  forming  pillars,  such 
as  shaft  pillars  and  dead-ends,  but  is  used  very  little  in  the 
operation  of  breaking  ore.  Its  principal  advantage  lies  in 
the  fact  that  it  is  straight-cut,  up-dip  work,  in  which  drilling 
and  blasting  can  readily  be  done,  the  face  clearing  itself  by 
gravity.  The  tendency  for  the  face  to  narrow,  due  to  the 
tight  corners  and  the  limited  space  in  which  work  must  be 
done,  especially  in  making  the  first  cut,  is  the  chief  objec- 
tion to  the  method. 

Longwall  Sloping  is  strictly  an  overhand  method  and  is 
extensively  employed  in  the  whole  range  of  dips  to  which 
overhand  stoping  can  be  successfully  applied. 

Probably  no  class  of  overhand  stoping  presents  more 
advantageous  conditions  for  the  work  of  breaking  ore  and 
its  disposal  than  does  longwall  stoping,  the  working  face 
being  level  and  adjacent  to  a  larger  number  of  chutes  than 
is  the  case  with  any  other  method.  Further,  cars  or  wheel- 
barrows can  be  employed  to  advantage  in  handling  and 
distributing  both  ore  and  waste,  but  are  applicable  only 
when  the  stope  is  filled  with  waste  or  ore,  or  there  are  inter- 
mediate levels  built  on  stulls.  Irregularities  in  the  deposit, 
such  as  barren  portions,  seriously  interfere  with  the  work 
and  often  require  a  change  in  method. 


METHODS  OF  STOPING  73 

BIBLIOGRAPHY  OF   METHODS   OF   STOPING 
GENERAL 

The  Witwatersrand  Goldfields,  by  S.  J.  Truscott.     Chapter  XV,  p.  335. 
Mining  Methods  at  Goldfield,  by  Claude  T.  Rice.     Eng.  and  Mining  Jour., 

vol.  92,  p.  797. 
Notes  on  Breaking  Ground,  by  T.  L.  Carter.     Eng.  and  Mining  Jour.,  vol. 

74,  P- 576. 
Notes  on  Rand  Mining,  by  Tom  Johnson.     Jour.  Chemical  Metallurgical 

and  Mining  Soc.  of  South  Africa,  March  1908,  p.  255. 
Methods  of  Stoping  on  the  Rand,  by  J.  A.  Wilkes.     Jour.  Chem.  Metallur- 
gical and  Mining  Soc.  of  South  Africa,  vol.  6,  p.  124. 
Stoping  in  the  Rand  Gold  Mines.     The  Gold  Mines  of  the  Rand,  by  Hatch 

and  Chalmers,  p.  127. 
Stoping  with  the  Air-hammer  Drill,  by  G.  E.  Walcott.     Eng.  and  Mining 

Jour.,  vol.  84,  p.  117. 
Los  Pilares  Mine,  by  Edward  M.  Robb,  Jr.     Mines  and  Minerals,  vol.  31, 

p.  106. 
Back-Stoping  vs.  Underhand  in  Large  Bodies  of  Iron  Pyrites,  by  J.  J. 

Rutledge.     Eng.  and  Mining  Jour.,  vol.  86,  p.  365. 

OVERHAND    STOPING 

Stoping  Methods  in  Mines  of  Ducktown  Basin,  by  John  Tyssowski.     Eng. 

and  Mining  Jour.,  vol.  89,  p.  463. 
Buffalo  Mine  and  Mill,  Cobalt,  by  W.  J.  Dobbins  and  H.  G.  S.  Anderson. 

Eng.  and  Mining  Jour.,  vol.  94,  p.  211. 
Stoping  Methods  at  the  Nevada  Wonder  Mine,  by  Thomas  M.  Smither. 

Mining  and  Scientific  Press,  vol.  no,  p.  757. 
Mining  Thick  Ore  bodies,  by  Ray  V.  Myers.     Mines  and  Minerals,  vol.  26, 

p.  407. 

Butte  Back-Filling  Stoping  Method.     Eng.  and  Mining  Jour.,  vol.  96,  p.  594. 
Cut  and  Fill  Method  in  Wide  Orebody.     Eng.  and  Mining  Jour.,  vol.  97,  p. 

SM. 
The  Panel  System  as  Applied  to  Metal  Mining,  by  H.  E.  West.     Eng.  and 

Mining  Jour.,  vol.  87,  p.  1177. 
Mining  Copper  at  Lake  Superior,  by  Claude  T.  Rice.     Eng.  and  Mining 

Jour.,  vol.  94,  p.  267. 
Mining  and  Stoping  Methods  in  the  Coeur  d'Alene,  by  John  Tyssowski. 

Eng.  and  Mining  Jour.,  vol.  90,  p.  452. 
Mining  Methods  at  Passagem,  by  A.  J.  Bensusan.     The  Mining  Magazine, 

vol.  3,  p.  379. 


74  ORE  MINING  METHODS 

Mining  Methods  Employed  at  Cananea,   Mexico,  by  Morris  J.  Elsing. 

Eng.  and  Mining  Jour.,  vol.  90,  p.  963. 
The  Clifton-Morenci  District  of  Arizona,  by  Wm.  L.  Tovote.     Mining  and 

Scientific  Press,  vol.  101,  p.  831. 
Mining  Methods  and  Practice,  by  E.  H.  Leslie.     Mining  and  Scientific 

Press,  vol.  108,  p.  43. 
The  Mount  Morgan  Mine,  Central  Queensland,  by  J.  Bowie  Wilson.     Eng. 

and  Mining  Jour.,  vol.  87,  p.  746. 
The  Method  of  Breast  Stoping  at  Cripple  Creek,  by  G.  E.  Walcott.     Eng. 

and  Mining  Jour.,  vol.  85,  p.  102. 

A  Michigan  Stoping  Method.     Mining  and  Scientific  Press,  vol.  109,  p.  18. 
Mining  Ore  from  Pillars,  by  H.  H.  Hodgkinson.     Eng.  and  Mining  Jour., 

July  29,  1916. 
The  Braden  Copper  Mines  in  Chile,  by  William  Braden.     Eng.  and  Mining 

Jour.,  vol.  84,  p.  1059. 
The  Caving  System  at  the  Menominee  Range,  by  Reginald  Meeks.   Eng. 

and  Mining  Jour.,  vol.  84,  p.  99. 
Stoping  Methods  at  the  North  Star  Mine,  by  L.  0.  Kellogg.     Eng.  and 

Mining  Jour.,  vol.  96,  p.  ion. 
Stoping  Methods  at  the  Golden  Cross  Mine,  by  A.  W.  Newberry.     Eng. 

and  Mining  Jour.,  vol.  98,  p.  193. 
The  Greenside  Lead  Mines,  Cumberland,  England,  by  E.  Thomas  Borlase. 

Eng.  and  Mining  Jour.,  vol.  85,  p.  297. 
Diamond  Mining  at  De  Beers.     Jour.  Chem.  Metallurgical  and  Mining  Soc. 

of  South  Africa,  vol.  7,  p.  227. 
Drifting  and  Stoping  at  Lake  Superior,  by  W.  R.  Crane.     Eng.  and  Mining 

Jour.,  vol.  82,  p.  645. 
Mining  Methods  at  Kimberly,  by  John  T.  Fuller.     Eng.  and  Mining  Jour., 

vol.  94,  p.  887;   also  p.  943. 
A  Modified  System  of  Back  Stoping  Employed  at  the  Dolores  Mine,  Mexico, 

by  J.  E.  Wilson.     Eng.  and  Mining  Jour.,  vol.  90,  p.  950. 
A  Method  of  Mining  in  Heavy  Ground,  by  W.  L.  Fleming.     Eng.  and 

Mining  Jour.,  vol.  88,  p.  375. 

UNDERHAND    STOPING 

A  Method  of  Underhand  Stoping,  by  Geo.  A.  Laird.     Eng.  and  Mining 

Jour.,  vol.  92,  p.  945. 
Departure  in  Sheet-Ore  Mining  in  the  Joplin  District,  by  Temple  Chapman. 

Eng.  and  Mining  Jour.,  vol.  87,  p.  942. 
Davis  Pyrites  Mine,  Massachusetts,  by  J.  J.  Rutledge.     Eng.  and  Mining 

Jour.,  vol.  82,  p.  673. 


METHODS  OF  STOPING  75 

Methods  of  Iron  Mining  in  Northern  Minnesota,  by  F.  W.  Denton.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  27,  p.  344;  also  pages  377-378. 
Mining  a  Pillar  of  Iron  Ore.     Eng.  and  Mining  Jour.,  vol.  94,  p.  879. 
Mining  Soft  Iron  Ore  Without  Timbers,  by  Stuart  R.  Elliott.     Mining  and 

Scientific  Press,  vol.  92,  p.  379. 
The  Present  Condition  of  Gold-Mining  in  the  Southern  Appalachian  States, 

by  H.  B.  C.  Nitze.     Trans.  Am.  Inst.  Mining  Engrs.,  vol.  25,  p.  773. 
Underground  Methods  on  the  Gogebic  Range,  by  Percival  S.  Williams. 

The  Mining  World,  Sept.  10,  1910,  p.  451. 
The  Mitchell  Slicing  System  at  Bisbee,  Arizona,  by  M.  J.  Elsing.     Eng. 

and  Mining  Jour.,  vol.  90,  p.  174. 

BREAST  STOPING 

Mines  and  Mill  of  the  Consolidated  Mercur  Company,  by  Roy  Hutchins 

Allen.     Eng.  and  Mining  Jour.,  vol.  89,  p.  1273. 
Notes  on  Caving  System  in  Northern  Iron  Mines,  by  Albert  H.  Fay.     Eng. 

and  Mining  Jour.,  vol.  88,  p.  961. 
Mining  Methods  at  the  Magpie  Iron  Mine,  Canada,  by  A.  Hasselbring. 

Bull.  No.  59,  Canadian  Mining  Inst.,  Mar.  1917,  p.  261. 
Mining  "Shut  Ground,"  by  J.  H.  Polhemus.     Mines  and  Minerals,  vol.  28, 

p.  171. 
Ground  Breaking  in  the  Joplin  District,  by  Dos  Brittain.     Eng.  and  Mining 

Jour.,  vol.  84,  p.  255. 

Methods  of  Mining  on  the  Mother  Lode,  California.     Mining  and  Scien- 
tific Press,  vol.  82,  p.  37. 
Extraction  of  Ore  From  Wide  Veins  or  Masses,  by  G.  D.  Delprat.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  21,  p.  89. 

SHRINKAGE  STOPING 

Mining  the  Treadwell  Lode,  by  T.  A.  Rickard.  Mining  and  Scientific 
Press,  vol.  97,  p.  85. 

"Shrinkage"  Stoping,  by  F.  Percy  Rolfe.  Mines  and  Minerals,  vol.  30, 
p.  210. 

Room  and  Pillar  Mining  at  Ray.     Eng.  and  Mining  Jour.,  vol.  97,  p.  1147. 

Mining  the  Prince  Consolidated  Ores,  by  D.  W.  Jessup.  Mining  and  Sci- 
entific Press,  May  31,  1913,  p.  820. 

Some  Features  of  Mining  Operations  in  the  Homestake  Mine,  Lead,  South 
Dakota,  by  Bruce  C.  Yates.  Mining  and  Scientific  Press,  vol.  88, 
p.  177. 

Stoping  at  Homestake  Mine  of  South  Dakota,  by  John  Tyssowski.  Eng, 
and  Mining  Jour.,  vol.  90,  p.  74. 


76  ORE  MINING  METHODS 

Filling  Methods  at  Sudbury,  by  W.  R.  Crane.  Eng.  and  Mining  Jour., 
vol.  91,  p.  1204. 

Los  Pilares  Mine,  Nacozari,  Mexico,  by  Courtney  De  Kalb.  Mining  and 
Scientific  Press,  vol.  100,  p.  887. 

Copper  Mining  in  Metcalf  District,  Arizona,  by  Peter  B.  Scotland.  Eng. 
and  Mining  Jour.,  vol.  90,  p.  118. 

Method  of  Mining  Swedish  Iron  Ore,  by  H.  de  Rauw.  Eng.  and  Mining 
Jour.,  vol.  91,  p.  409. 

Mining  Methods  at  the  Pilares  Mine,  Nacozari,  Mexico.  Eng.  and  Min- 
ing Jour.,  vol.  94,  p.  686. 

Mining  at  Santa  Barbara,  Mexico,  by  F.  J.  De  Wilde.  Mining  and  Scien- 
tific Press,  vol.  no,  p.  521. 

Mining  at  Miami,  Arizona,  by  R.  L.  Herrick.     Mines  and  Minerals,  vol. 

30,  P-  75i- 

Mining  Low-Grade  Copper  Ore  at  Ray  Consolidated,  by  Alec  N.  Penny. 
Eng.  and  Mining  Jour.,  vol.  99,  p.  767. 

The  Cresson  Mine,  by  R.  L.  Herrick.     Mines  and  Minerals,  vol.  31,  p.  735. 

The  Miami-Inspiration  Ore-Zone,  by  C.  F.  Tolman,  Jr.  Mining  and  Sci- 
entific Press,  vol.  99,  p.  646. 

Copper  Deposits  of  Globe-Kelvin  District,  by  Edwin  Higgins.  Eng.  and 
Mining  Jour.,  vol.  89,  p.  813. 

Mining  Methods  in  the  Waihi  Mine,  by  Jas.  L.  Gilmour  and  \V.  N.  John- 
ston. Mining  and  Scientific  Press,  vol.  105,  p.  789. 

Low  Cost  of  Mining  on  the  Mother  Lode,  by  William  G.  Devereux.  Eng. 
and  Mining  Jour.,  vol.  92,  p.  546. 

Notes  on  the  Gold-Mines  of  Zaruma,  Ecuador,  by  J.  Ralph  Finlay.  Trans. 
Am.  Inst.  Mining  Engrs.,  vol.  30,  p.  248. 

Shrinkage  Stoping  on  the  Rand,  by  G.  Hendrick  Smith.  The  Mining  Mag- 
azine (London),  vol.  4,  p.  145. 

RILL-STOPING 

The  Rill  System  of  Stoping,  by  J.  Bowie  Wilson.     Eng.  and  Mining  Jour., 

vol.  92,  p.  1000. 
Stoping  without  Timbers,  by  Mark  Ehle.    Mines  and  Minerals,  vol.  28, 

p.  460. 
Cut  and  Fill  Stoping  at  the  Copper  Queen.     Eng.  and  Mining  Jour.,  vol. 

98,  p.  701. 
Stoping  at  the  Calamon  Mine,  by  C.  P.  Corbett.    Eng.  and  Mining  Jour., 

vol.  93,  p.  637. 
Stoping  Methods  at  Kalgoorlie,  by  J.  Cheffirs.     Mining  and  Scientific  Press, 

vol.  100,  p.  391. 


METHODS  OF  STOPING  77 

The  Superior  and  Boston  Mine,  by  R.  L.  Herrick.     Mines  and  Minerals, 

Vol.  31,  p.  112. 
Stoping  Systems  at  Broken  Hill,  Australia,  by  A.  J.  Moore.      Mines  and 

Minerals,  vol.  27,  p.  433. 

RESUING 

Resuing  and  Back  Stoping,  by  J.  F.  Whitton.    Jour.  Chem.  Metallurgical 

and  Mining  Soc.  of  South  Africa,  vol.  7,  p.  367. 
Resuing  in  Mining,  by  A.  Richardson.     Jour.   Chem.  Metallurgical  and 

Mining  Society  of  South  Africa,  vol.  8,  p.  48. 


CHAPTER   IV 
METHODS    OF    HANDLING    ORE    IN    STOPES 

The  ways  and  means  employed  in  handling  ore  in  slopes 
are  almost  as  varied  as  the  methods  of  stoping,  and  in  fact 
the  handling  of  ore  in  the  working  places  often  has  a  con- 
trolling influence  on  the  methods  of  extracting  the  mineral. 
As  the  methods  of  stoping  are  fundamental  operations  in  the 
extraction  of  ores,  so  in  like  manner  the  methods  of  handling 
the  ore  in  the  usual  stoping  operations  are  similar  to  all 
other  methods  in  use  regardless  of  what  kind  of  mineral  or 
metal  is  mined  or  how  it  is  mined. 

From  the  standpoint  of  handling  ore  the  work  may  be 
divided  into  two  classes  as  in  open  and  closed  s topes.  The 
former  comprises  the  simplest  class  of  work,  while  the  latter 
is  by  far  the  most  important  both  as  to  kind  and  extent 
of  operations. 

Open  stope  work  may  include  practically  all  methods  of 
stoping,  but  is  usually  applied  to  moderate  inclinations  and 
especially  such  that  the  broken  ore  will  move  downward  by 
gravity  with  or  without  assistance.  The  best  results  are 
secured  when  the  deposit  dips  at  an  angle  of  38  to  40°,  or 
is  equal  to  the  angle  of  repose  of  the  broken  ore.  With  a 
fairly  even  footwall  or  floor  standing  at  a  proper  angle, 

ore  can  be  readily  transferred  for  a  distance  of  several 

78 


METHODS  OF  HANDLING   ORE  IN  STOPES 


79 


hundred  feet,  and  that  too  regardless  of  whether  overhand 
or  underhand  stoping  is  done. 

HANDLING  ORE  IN  OPEN  STOPES 

On  reaching  the  bottom  of  the  stope  the  ore  is  either 
shoveled  into  cars  standing  on  the  level  tracks  or  may  be  run 
on  to  docks  from  which  it  is  shoveled  into  cars.  The  latter 
method  is  preferable  from  the  standpoint  of  shoveling,  but  is 
not  as  extensively  employed  as  the  former.  (See  Fig.  19.) 


FIG.  19.  — Ore-Loading  Dock  in  Open  Stope. 

When  the  footwall  is  somewhat  uneven,  or  the  dip  is 
several  degrees  less  than  the  angle  of  repose  of  the  ore, 
it  may  be  found  necessary  to  assist  gravity  in  the  trans- 
ference of  the  ore  either  by  actually  shoveling  or  raking,  or 
by  placing  it  in  chutes  of  wood  or  metal,  the  angle  of  which 
is  greater  than  that  of  the  stope  floor,  or  the  friction  less 
than  that  between  the  ore  and  stope  floor. 


8o  ORE  MINING  METHODS 

Shoveling  is  still  largely  employed  in  certain  districts 

• 

and  with  both  overhand  and  underhand  work.  Sheets  of 
boiler  plate  may  be  laid  on  the  stope  floor  as  in  coal  mining, 
extending  from  the  bottom  of  the  stope  to  the  working  face, 
the  sheets  overlapping  shingle-fashion.  Better  still  is  the 
use  of  curved  sheet-metal  chutes,  which  may  be  placed 
similarly  to  the  plain  sheets,  but  are  easier  to  handle  and 
consequently  more  care  is  usually  taken  in  mounting  them 
with  regard  to  both  direction  and  inclination.  S topes  with 
inclinations  falling  to  as  much  as  15°  below  the  angle  of 
repose  may  have  the  ore  handled  without  difficulty  by  such 
means.  In  order  that  the  momentum  of  the  ore  may  be 
checked  somewhat  before  entering  the  car  at  the  bottom  of 
the  stope,  it  is  customary  to  materially  reduce  the  slope  of 
the  last  two  or  three  sections  of  chute.  (See  Fig.  20.) 

The  use  of  metal  chutes  may  be  extended  to  stopes  of 
very  slight  dip  by  giving  them  a  shaking  motion,  while 
the  monorail  and  chain  conveyors  are  now  being  employed 
to  transfer  mineral  for  considerable  distances  in  mines  and 
under  practically  all  degrees  of  inclination,  even  reverse 
grades. 

A  unique  method  of  overcoming  an  exceedingly  rough 
and  irregular  floor  of  stope  is  that  in  use  in  the  North  Star 
mines,  Grass  Valley,  California.  The  gravity  plane  idea 
as  employed  in  coal  mines  has  been  adopted.  A  double  line 
of  track  is  laid  directly  up  the  dip  of  the  stope  at  the  upper 
end  of  which  is  set  a  post  to  which  is  attached  a  three- wheeled 
device  called  a  '  go-devil. '  A  steel  cable  passes  from  the 
bottom  to  the  top  of  the  plane,  being  attached  to  an  empty 


METHODS  OF  HANDLING  ORE  IN  STOPES 


81 


03 

u 

bJ3 
C 

13 

o 


82  ORE  MINING  METHODS 

car  below  and  after  passing  around  the  three  grooved  wheels 
of  the  go-devil  extends  and  is  attached  to  a  loaded  car  at  the 
top  of  the  plane.  The  go-devil  is  controlled  by  a  hand- 
brake, and  when  pushed  off  the  landing  the  loaded  car  runs 
to  the  level  below,  drawing  up  the  empty  car.  This  system 
has  proved  very  successful  and  is  extensively  employed  in 
these  mines. 

In  deposits  of  slight  inclination,  where  breast  stoping  is 
employed,  cars  are  run  to  the  face  on  track  laid  diagonally 
up  the  stope  and  maintaining  a  grade  such  that  the  cars 
can  be  controlled  by  brakes  or  sprags.  The  character  of 
the  ore  has  an  important  bearing  upon  the  distance  that  it 
will  travel  from  the  face  on  being  blasted  down.  This  can 
be  illustrated  to  good  advantage  by  citing  the  conditions 
existing  in  the  hard  iron  ore  mines  of  the  Birmingham  dis- 
trict, Alabama.  To  a  certain  depth  below  the  outcrop  the 
ore  has,  in  many  places,  been  rendered  more  or  less  soft  by 
percolating  waters;  below  this  point  the  ores  are  still  hard. 
Stopes  carried  on  moderate  inclinations  in  the  hard  ore  will 
deliver  a  large  part  of  it  at  the  bottom  of  the  stope,  as  it 
breaks  coarse  and  rolls  well;  with  the  soft  ore  the  reverse 
is  the  case,  the  ore  breaks  moderately  fine  and  slumps  down 
close  to  the  working  face,  necessitating  the  employment  of 
cars  throughout  the  stope.  (See  Fig.  21.) 

HANDLING  ORE  IN  CLOSED  STOPES 

Closed  stope  work  as  distinguished  from  open  stope  work 
has  the  levels  roofed  over  and  protected  by  pillars  of  mineral, 
by  stulls  and  lagging  covered  in  turn  with  waste,  by  pack- 


METHODS  OF  HANDLING  ORE  IN  STOPES 


84  ORE  MINING  METHODS 

walls,  etc.  (Fig.  2.)  In  wide  veins  or  massive  deposits 
the  levels  may  be  protected  by  sets  and  square-sets  held  in 
place  by  stulls,  filling,  etc.  (See  Figs,  i  and  4.)  In  either 
case  connection  is  made  between  the  levels  and  open  stopes 
by  passages  commonly  known  as  chutes,  mill-holes,  passes, 
etc.  (Figs,  ii  and  14.) 

In  both  overhand  and  underhand  stoping,  pillars  are 
occasional^  left  directly  above  the  levels  which  serve  the 


FIG.  22.  — Block-Hole  Fitted  with  Chute  for  Passing  Ore  through  Pillar. 

double  purpose  of  support  and  protection  to  the  levels. 
Holes  called  '  block-holes '  are  cut  through  these  pillars  at 
intervals  of  25  ft.  or  more  the  ore  being  passed  through  them 
to  the  cars  below.  (See  Fig.  22  and  stope  B-i,  Fig.  13.) 
A  line  of  stulls  may  be  employed  in  place  of  pillars  and  serves 


METHODS  OF  HANDLING  ORE  IN  STOPES  85 

the  same  purpose.  On  moderately  flat  dips,  and  where 
there  is  little  or  no  waste  to  be  disposed  of,  the  ore  may  be 
transferred  to  the  bottom  of  the  stope  as  in  open  stopes,  the 
advantages  being  that  the  levels  are  not  cumbered  by  ore 
running  down  from  the  stopes  above  and  that  the  cars  are 
loaded  by  gravity. 

When  stulls  are  used  the  line  of  stulls  and  covering  of 
lagging  may  at  intervals  be  extended  in  a  diagonal  direction 
for  some  distance  up  the  stope,  meeting  similar  lines  run  in 
opposite  directions.  This  arrangement  is  called  i  winged 
stulls'  and  is  useful  in  collecting  the  ore  sliding  downward 
and  in  delivering  it  to  the  chute  gates  extending  through 
the  line  of  stulls.  (See  Fig.  23.)  By  this  arrangement 
chutes  may  be  placed  further  apart. 

CHUTES  AND  MILL-HOLES 

In  stopes  where  a  filling  of  waste  or  ore  is  employed,  built- 
up  chutes,  consisting  of  either  walled-up,  well-like  openings, 
cribbed  passages,  or  passages  one  side  of  which  is  wall  rock 
(usually  foot-wall)  the  other  sides  timber,  are  extended 
through  the  filling  to  the  stope  above.  These  passages, 
usually  the  timbered  ones,  are  often  made  with  two  com- 
partments —  one  for  ore,  the  other  for  a  manway. 

Stope-chutes  are  formed  in  the  ore  or  rock  at  the  side  of 
stopes  and  serve  to  draw  off  the  surplus  ore  (Fig.  24). 

In  narrow  veins  the  chutes  usually  follow  the  dip  very 
closely  and  are  often  built  on  the  foot-wall,  while  in  wider 
veins  they  may  be  vertical  or  inclined  at  whatever  angle 
seems  best  suited  to  the  character  of  the  ore  and  the  chute 


86 


ORE  MINING  METHODS 


"2 

bJD 


METHODS  OF  HANDLING  ORE  IN  STOPES 


FIG.  24.  —  Stope-Chute  for  Handling  Excess  Ore  in  Stope. 
(Modeled  after  Sketch  in  Mining  and  Scientific  Press,  vol.  98,  p.  556.) 


FIG.  25.  — Chutes  Used  in  Developing  a  Shrinkage  Stope  with  Cribbed  Chute 
and  Manway.     (Modeled  from  Sketch  by  J.  E.  Wilson.) 


88  ORE  MINING  METHODS 

lining.  (Figs.  1 1  and  25.)  In  vertical  chutes  of  small  section 
there  is  danger  of  their  becoming  choked  up,  requiring  the 
use  of  explosives,  which  must  be  used  with  care  to  prevent 
damage  to  chute  walls.  Broken-sloped  chutes  are  preferable 
when  long  lines  must  be  employed.  The  branched  chutes 
occasionally  used  with  square-sets  in  the  mines  of  the  Cceur 
d'Alene  District  are  good  examples  of  broken-sloped  chutes. 
Several  portions  of  a  stope  may  be  served  by  branches  ex- 
tending at  various  angles  and  in  a  number  of  directions  from 
the  main  chute;  the  movement  of  ore,  especially  in  steep 
chutes,  can  be  controlled  to  better  advantage  by  their  use. 
Broken-sloped  chutes  driven  in  solid  ground  are  found  to 
give  better  results  when  the  first  portion  above  the  point  of 
delivery  of  ore  is  vertical,  the  remaining  portion  standing  at 
an  angle  of  50°  or  more  from  the  vertical.  It  is  claimed  for 
such  chutes  that  the  change  in  direction  prevents  packing 
of  ore  and  choking  of  chutes.  This  arrangement  proved 
very  successful  in  the  caving  system  employed  in  the  B  ing- 
ham  Canyon  mines. 

Broken-slope  chutes  also  serve  a  useful  purpose  in  discharg- 
ing into  ore  bins,  preventing  choking  of  chutes  and  bins  and 
relieving  the  gates  from  excessive  pressure.  (Figs.  1 1  and  26.) 

At  the  lower  end  of  the  chutes  must  be  some  device  not 
only  for  directing  the  ore  into  cars  but  for  controlling  the 
flow  of  ore  from  the  chutes.  This  is  accomplished  by  having 
a  sloping  spout  attached  to  the  bottom  of  the  chute,  provided 
with  a  gate  and  controlled  by  a  hand  lever.  Unless  con- 
structed of  proper  section  and  given  a  suitable  slope  the  ore 
will  become  jammed  in  and  will  not  discharge.  A  method 


METHODS  OF  HANDLING  ORE  IN  STOPES  89 

of  discharging  ore  from  stopes,  often  used  in  the  Australian 
mines,  goes  by  the  name  of  '  chinaman  chute. '  The  china- 
man chute  consists  of  a  platform,  built  several  feet  below 
the  line  of  stulls,  containing  a  number  of  openings  through 
which  ore  is  discharged  into  cars  below.  The  openings  are 
usually  provided  with  grizzlies  for  sizing  the  ore.  An 


FIG.  26.  —  Broken-Slope  Chute  and  Ore  Pocket  as  Used  in  the  Copper  Queen 
Mine.    (Modeled  after  Sketch  by  F.  G.  Sherman.) 

opening  in  the  lagging  permits  the  ore  to  flow  from  the 
stope  on  to  the  platform,  where  it  piles  up  until  the  opening  in 
the  stull  lagging  is  reached.  On  removing  the  covers  to  the 
platform  openings  the  ore  falls  into  the  cars,  and  when  a 
certain  amount  has  been  drawn  off  a  movement  of  the  ore 
in  the  stope  again  takes  place.  The  flow  of  ore  from  the 
stope  is  then  automatically  controlled  by  the  operation 


90  ORE  MINING  METHODS 

of  loading  cars.     (See  Fig.  27.)     Another  type  of  chinaman 
chute  is  shown  in  Fig.  28. 

Handling  ore  at  the  working  face  may  be  done  by  hand, 
i.e.,  by  shoveling,  but  when  this  is  the  practice  the  chutes  or 
mill-holes  must  be  placed  closer  together  and  should  not  ex- 
ceed 25  ft.  apart.  In  wide  veins  where  the  s topes  are  large, 


FIG.  27. — A  Chinaman  Chute  as  Used  in  Australian  Mines. 

wheelbarrows  may  be  employed,  also  cars;  in  which  case  the 
chutes  may  be  spaced  much  further  apart,  as  from  35  to  55  ft. 
Other  devices  might  be  described  and  cases  cited  illus- 
trating the  uses  of  chutes  and  loading  mechanisms,  but  those 
given  will  serve  to  show  the  general  methods  of  procedure 
and  the  importance  of  efficient  methods  of  handling  ore. 


FIG.  28.  —  Chinaman  Ore  Chute  Provided  with  Grizzly. 


B.  —  Chute  Used  for  Handling  Ore  in  the  Miami  Copper  Mine. 

(Modeled  after  Sketch  by  David  B.  Scott.)  91 


92  ORE  MINING  METHODS 

BIBLIOGRAPHY  OF  HANDLING  ORE  IN  MINES 
GENERAL 

An  Economical  Mining  Method.     Mining  and  Scientific  Press,  vol.  85,  p. 

366. 
Ore  Breaking  at  Lake  Superior,  by  W.  R.  Crane.     Eng.  and  Mining  Jour., 

vol.  82,  p.  767. 
Iron  Mining  in  the  Birmingham  District,  Ala.,  by  W.  R.  Crane.     Eng. 

and  Mining  Jour.,  vol.  79,  p.  274. 

The  Witwatersrand  Gold  Fields,  by  S.  J.  Truscott.     Chapter  IX,  p.  197. 
Handling  Ore  in  the  Stopes,  by  D.  T.  Williams.     Mining  and  Scientific 

Press,  vol.  92,  p.  183;  Mines  and  Minerals,  vol.  27,  p.  188. 
Ore  Delivery  from  Stopes,  by  E.  L.  Le  Fevre.      Mining  and  Scientific  Press, 

vol.  88,  p.  280. 

MILL-HOLES 

Cananea   Caving  and   Slicing   Systems,   by  R.   L.   Herrick.     Mines   and 

Minerals,  vol.  30,  p.  23. 
Baltic  Method  of  Mining,  by  Claude  T.  Rice.     Eng.  and  Mining  Jour., 

vol.  93,  p.  897. 
Cylindrical  Wooden  Ore-Passes,   by  Andrew  Fairweather.     Mining  and 

Scientific  Press,  vol.  108,  p.  257. 
Mining  and  Stoping  Methods  in  the  Coeur  d'Alene,  by  John  Tyssowski. 

Eng.  and  Mining  Jour.,  vol.  90,  p.  452. 
Skip-loading  Arrangement  at  the  Herald  Mine,  Joplin,  Mo.      Eng.  and 

Mining  Jour.,  vol.  89,  p.  1004. 

CHUTES   AND    CHUTE    GATES 

Methods  of  Iron  Mining  in  Northern  Minnesota,  by  F.  W.  Denton.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  27,  p.  344. 
Chute  for  Handling  Boulders,  by  Henry  S.  Volker.     Eng.  and  Mining  Jour., 

vol.  98,  p.  65. 
A  Substantial  Ore  Chute,  by  H.  H.  Hodgkinson.     Eng.  and  Mining  Jour., 

vol.  99,  p.  861. 
A  Standard  Ore  Chute,  by  S.  S.  Arentz.     Eng.  and  Mining  Jour.,  vol.  92, 

p.  1216. 

Cananea  Arc  Type  Gate.     Eng.  and  Mining  Jour.,  vol.  92,  p.  933. 
The  Treadwell  Group  of  Mines,  Douglas  Island,  Alaska,  by  Robt.  A.  Kinzie. 

Trans.  Am.  Inst.  Mining  Engrs.,  vol.  34,  p.  334. 
Chutes  for  Ore-filled  Stopes.     Eng.  and  Mining  Jour.,  vol.  88,  p.  472. 
Steel  Skip  Loading  Chute.     Eng.  and  Mining  Jour.,  vol.  90,  p.  1292. 


METHODS  OF  HANDLING  ORE  IN  STOPES  93 

Skip  Loading  Chute.     Eng.  and  Mining  Jour.  vol.  89,  p.  256;  Ibid,  vol.  87, 

p.  254. 
Methods  of  Mining  the  Grandby  Orebodies,  by  C.  M.  Campbell.     Eng. 

and  Mining  Jour.,  vol.  87,  p.  252. 
Chute  for  Rough  Ore  in  Shrinkage  Stopes.     Eng.  and  Mining  Jour.,  vol. 

88,  p.  422. 

Finger-Chutes.     Mining  and  Scientific  Press,  vol.  98,  p.  314. 
The  Finger-Chute,  by  T.  A.  Rickard.     Mining  and  Scientific  Press,  vol. 

97,  P- 538. 

A  Finger  Chute.     Eng.  and  Mining  Jour.,  vol.  88,  p.  1130. 
Bulkhead  Ore  Chutes.     Eng.  and  Mining  Jour.,  vol.  89,  p.  1310. 
Ore  Chute  and  Gate,  by  J.  R.  Thoenen.     Eng.  and  Mining  Jour.,  vol.  98, 

P-957- 
Types  of  Chutes  and  Chute  Gates,  by  Albert  E.  Hall.     Eng.  and  Mining 

Jour.,  vol.  99,  p.  738. 
Sliding  Chute  Gate  with  Lever  Action.     Eng.  and  Mining  Jour.,  vol.  96, 

P- 452. 

Bulldozing  Chute  and  Underswing  Gate,  by  G.  J.  Jackson.     Eng.  and  Min- 
ing Jour.,  vol.  96,  p.  735. 
Emergency  Gate,  by  P.  B.  McDonald.     Mining  and  Scientific  Press,  vol. 

io8,p.  935. 

Ore  Gate  at  the  Mammoth  Mine,  by  Chas.  W.  Morse.     Mining  and  Scien- 
tific Press,  vol.  106,  p.  743. 
Gates  for  Ore  Chutes,  by  K.  Baumgarten.     Eng.  and  Mining  Jour.,  vol. 

92,  p.  740. 
Chute  Used  in  the  Bingham  Copper  Mines,  by  D.  W.  Jessup.     Eng.  and 

Mining  Jour.,  vol  97,  p.  413. 

Opening  Ore  Passes,  by  W.  J.  Nicol.     Eng.  and  Mining  Jour.,  vol.  94,  p.  1216. 
Mining  Methods  in  the  Vermillion  Iron  District,  Minnesota,  by  Kirby 

Thomas.     Mining  and  Scientific  Press,  vol.  88,  p.  133. 
Eliminating   Shoveling  in   Square-Set   Stopes.     Eng.   and   Mining  Jour., 

vol.  90,  p.  59. 
Caving  System  at  the  Ohio  Copper  Mine,  by  F.  Sommer  Schmidt.     Mining 

and  Scientific  Press,  vol.  no,  p.  361. 

Chute  Stope.     Mining  and  Scientific  Press,  vol.  98,  p.  556. 
Boston   Consolidated,   Bingham   Canyon,   Utah,  by   Courtney  De  Kalb. 

Mining  and  Scientific  Press,  vol.  98,  p.  553. 
Handling  Ore  in  Narrow  Square-set  Stopes,  by  Frank  R.  Edwards.     Eng. 

and  Mining  Jour.,  vol.  91,  p.  949. 

The  Chinaman  Chute.     Trans.  Inst.  Mining  and  Metallurgy,  vol.  18,  p.  294. 
A  Modified  "Chinaman."     Eng.  and  Mining  Jour.,  vol.  89,  p.  1215. 
The  "Chinaman"  Ore  Chute.     Mining  and  Scientific  Press,  vol.  96,  p.  667. 


94  ORE  MINING  METHODS 

ORE   POCKETS 

Cutting  a  Station  and  Pocket  in  Ore,  by  L.  D.  Davenport.     Eng.  and  Mining 

Jour.,  vol.  94,  p.  733. 
A  Hancock  Shaft  Station,  by  Claude  T.  Rice,  Eng.  and  Mining  Jour., 

vol.  95,  p.  888. 

Three-Stage  Hoisting  System.     Eng.  and  Mining  Jour.,  vol.  96,  p.  448. 
Underground  Crushing  and  Loading  Station,  by  R.  C.  Warriner.     Eng. 

and  Mining  Jour.,  vol.  96,  p.  118. 
Underground  Ore  Bin,  by  Chas.  W.  Henderson.     Mines  and  Minerals,  vol. 

31,  P.  730. 

Concrete  Hoisting  Pockets.     Eng.  and  Mining  Jour.,  vol.  98,  p.  612. 
Ore-Chute  Side  Pocket,  by  Lewis  B.  Pringle.     Eng.  and  Mining  Jour., 

vol.  98,  p.  389. 
Hydraulically  Operated  Skip  Loading  Pockets,  by  Clarence  M.  Haight. 

Eng.  and  Mining  Jour.,  vol.  98,  p.  17. 
Underground  Ore  Bins,  by  Hatch  and  Chalmers.     The  Gold  Mines  of  the 

Rand,  Chapter  VI,  p.  132. 
Development  Methods  at  Mineville,  by  Gus  C.  Stoltz.     Eng.  and  Mining 

Jour.,  vol.  94,  p.  792. 
Method   of   Loading  Skips,  by  Guy  C.  Stoltz.     Eng.  and  Mining  Jour., 

vol.  92,  p.  1075. 

Loading  Bin  for  Skips,  by  L.  E.  Ives.    Eng.  and  Mining  Jour.,  vol.  91,  p.  1195. 
A  Single  Balanced  Skip  for  Lowering  in  Inclined  Workings,  by  S.  A.  Wor- 
cester.    Eng.  and  Mining  Jour.,  vol.  83,  p.  173. 
An  Underground  Ore  Pocket,  by  E.  S.  Dickinson.     Eng.  and  Mining  Jour., 

vol.  91,  p.  900. 
Transvaal  Gold  Mining  —  Present  and  Future  Methods,  by  F.  H.  Hatch. 

Eng.  Magazine,  vol.  43,  p.  505. 
Method  of  Hanging  Chute  Door  and  Lever.    Eng.  and  Mining  Jour.,  vol. 

94,  P-  539- 

CHUTE  CONVEYORS  AND  PLANES 

Hanging  Chutes,  by  L.  D.  Davenport.  Eng.  and  Mining  Jour.,  vol.  94,  p.  349. 
Flat  Dips  and  Chute  Conveyors.  Eng.  and  Mining  Jour.,  vol.  95,  p.  565. 
Stoping  Methods  at  the  North  Star  Mine,  by  L.  O.  Kellogg.  Eng.  and 

Mining  Jour.,  vol.  96,  p.  ion. 
Conveyor  Belts  for  Distributing  Filling.     Eng.   and  Mining  Jour.,  vol. 

97,  P.  759- 
Improvement  in  Underground  Trolley  Conveyors,  by  E.  M.  Weston.     Eng. 

and  Mining  Jour.,  vol.  96,  p.  401. 
Underground  Ore  Handling  at  Lake  Superior,  by  W.  R.  Crane.     Eng.  and 

Mining  Jour.,  vol.  82,  p.  695. 


CHAPTER  V 

MINING   IN    NARROW   AND   MODERATELY  WIDE 
VEINS    AND    BEDDED    DEPOSITS 

INTRODUCTION 

As  the  methods  of  breaking  down  ore  or  stoping  have 
already  been  discussed  and  their  relation  to  the  handling  of 
ore  in  the  working  places  and  the  development  work  of  the 
mine  has  been  indicated,  the  methods  of  mining  may  now 
be  taken  up.  Mining  is  the  working  of  mineral  deposits 
and  includes  all  phases  of  work  pertaining  thereto,  as  pros- 
pecting, development,  exploration  and  extraction  of  ore. 
Methods  or  systems  of  mining,  as  generally  considered, 
consist  of  the  development  and  working  of  deposits,  but  by 
common  usage  the  meaning  of  the  terms  has  been  extended 
and  now  includes  the  working  of  deposits,  support  of  work- 
ings and  handling  of  the  ore.  The  expressions  overhand 
and  underhand  mining,  square-set  mining,  the  top-slice  and 
sub-drift  cavings  systems  of  mining,  etc.,  illustrate  the 
indefiniteness  of  such  a  designation  as  method  or  system,  but 
it  must  be  admitted  indicate  the  salient  features  of  the  work 
done,  and  at  the  same  time  are  probably  less  cumbersome 
than  other  more  exact  and  discriminating  designations. 

In  the  following  pages  are  given  methods  of  mining  appli- 
cable to  narrow  and  moderately  narrow  veins  and  bedded 
deposits  and  they  are  considered  in  order  of  their  simplicity 

95 


96  ORE  MINING  METHODS 

and  ease  of  working.  The  following  methods  are  discussed : 
mining  bedded  deposits  by  the  use  of  props;  mining  mineral 
veins  by  the  use  of  stulls;  mining  mineral  veins  by  the  use 
of  square-sets;  mining  mineral  veins  by  the  use  of  filling; 
and  mining  veins  and  bedded  deposits  by  caving. 

An  endeavor  has  been  made  to  limit  the  discussion  of 
methods  of  mining  in  this  chapter  to  veins  and  deposits  not 
exceeding  35  to  40  ft.  in  width  and  particularly  to  much 
narrower  ones,  but  it  has  been  found  difficult  to  do  this.  A 
few  descriptions  are  given  of  deposits  averaging  35  ft.  and 
over,  where  good  descriptions  of  narrower  veins  were  not 
available  from  the  writer's  personal  experience  or  from 
technical  literature. 

MINING  BEDDED  DEPOSITS  BY  THE  USE  OF  PROPS 
Underhand  Sloping  with  Props 

The  iron  mines  of  the  Birmingham  district,  Alabama,1 
are  good  illustrations  of  the  application  of  overhand  stoping 

1.  Birmingham,  Ala.    to  bedded  deposits  of  slight  and  moder- 

2.  iron  ore.  ate  inclinations.     The  strata  worked  vary 

3.  Bedded  deposit. 

4.  Thickness  10  to    from  io  to  2o  ft.  in  thickness,  while  the 

dip  ranges  from  8  to  50°  and  above, 
but  averages  about  12°.  The  ore  occurs  in  the  Clinton 
formation  of  the  Red  Mountains;  it  is  hematite  and  was 
originally  very  hard,  but  owing  to  the  leaching  action  of 
percolating  waters  the  upper  portions  have  been  changed 
more  or  less  into  a  soft  ore,  due  probably  to  the  loss  of  lime. 

1  Iron  Mining  in  the  Birmingham  District,  Alabama,  by  W.  R.  Crane, 
Eng.  and  Mining  Jour.,  Vol.  79,  p.  274. 


MINING  IN  VEINS  AND    BEDDED  DEPOSITS  97 

The  irregularity  of  the  limit  of  soft  ore  is  shown  in  Fig.  21. 
The  formations  overlying  the  iron  ore  are  largely  sandstones, 
while  shale  occurs  below. 

These  mines  are  opened  by  slopes  or  inclined  shafts  in 
the  deposit,  from  which  at  intervals  of  50  to  60  ft.  levels  are 
driven.  The  levels  are  run  at  a  width  of  12  to  15  ft.  for  a 
distance  of  100  to  150  ft.,  beyond  which  point  they  are  in- 
creased to  20  or  30  ft.,  forming  low  stopes.  On  both  sides 
of  the  shaft,  pillars  are  left  which  vary  in  width  from  60 
to  75  ft.  The  width  of  the  pillars  is  definitely  determined 
by  airways  and  manways  which  parallel  the  shaft.  Along 
the  levels  break-throughs  are  formed  in  the  arch  pillars, 
making  connection  between  adjacent  stopes,  and  serve  as 
means  of  inlet  and  exit  to  and  from  the  stopes  as  well  as  a 
convenience  in  carrying  air  lines  to  all  parts  of  them;  ven- 
tilation is  also  facilitated. 

The  stopes  having  been  driven  to  the  limit  of  economic 
handling  of  ore  on  the  levels,  the  direction  of  working  is 
reversed  and  the  ore  left  standing  in  pillars  during  the  first 
part  of  the  operations  is  now  removed.  The  method  of 
mining  then  resolves  itself  into  room-and-pillar  work  by 
advancing  and  retreating,  the  larger  part  of  the  ore  being 
mined  from  the  pillars  and  therefore  by  pillar-drawing.  The 
drawing  of  pillars  may  be  accomplished  by  cutting  off 
longitudinal  or  transverse  slices;  the  former  when  the  ore 
is  moderately  soft  and  the  stopes  are  high,  the  latter  when 
hard  or  moderately  hard  ore  is  worked  and  the  levels  are 
close  together. 

Hard  ore  breaks  up  into  relatively  large  pieces  which 


98  ORE  MINING  METHODS 

under  the  impulse  of  the  blast  readily  finds  its  way  to  the 
bottom  of  the  stopes;  while  the  soft  ore,  which  is  more  or 
less  earthy  in  character,  slumps  down  arid  does  not  travel 
far  from  the  working  face.  It  is  evident  then  that  when 
soft  ore  is  mined  either  the  levels  must  be  driven  closer  to- 
gether or  the  cars  must  be  run  up  into  the  stopes  to  the 
working  face;  in  fact  both  methods  are  employed,  but  as 
levels  should  not  be  run  too  close  together,  even  if  formed 
by  stoping  as  it  is  an  expensive  operation,  the  running  of 
cars  into  the  stopes  is  usually  preferred.  (See  Fig.  29.) 

With  low  dips  the  method  of  attack,  although  up  the 
dip,  as  in  overhand  stoping,  resembles  more  closely  breast 
stoping  and  has  all  the  advantages  of  such  work. 

Owing  to  the  comparatively  slight  inclination  of  the  de- 
posit practically  the  whole  weight  of  the  roof  must  be  sup- 
ported, therefore  necessitating  considerable  support,  which  is 
provided  by  an  extensive  use  of  props.  These  props  vary 
from  8  to  14  and  16  in.  in  diameter,  being  used  in  the  rough, 
and  are  spaced  from  6  to  25  ft.  apart  according  to  the  con- 
dition of  the  roof.  The  drawing  of  pillars  in  the  upper  levels 
and  the  caving  that  results  relieves  the  pressure  to  a  certain 
extent  in  the  lower  levels,  but  with  greater  depth  of  working 
the  problem  of  support  will  become  more  serious  and  may 
require  a  change  in  the  method  of  working. 

The  advantages  and  disadvantages  of  the  method  de- 
scribed above  have  already  been  given  under  the  respective 
heads  of  overhand  and  breast  stoping,  but,  as  previously 
indicated,  a  serious  disadvantage  is  the  high  cost  of  develop- 
ment resulting  from  running  levels  close  together,  but  it  is 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS 


99 


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ioo  ORE  MINING   METHODS 

claimed  that  this  is  largely  offset  by  the  thickness  of  the 
workable  strata  and  the  large  outputs  obtained  from  small 
areas.  The  cost  of  timber  is  also  a  large  item. 

MINING  MINERAL  VEINS  BY  THE  USE  OF  STULLS 

Stull-floor  Method 

Of  the  various  methods  of  maintaining  stopes  employed 
in  the  Tonopah  mines,  the  use  of  stulls  is  probably  the 

1.  Tonopah    Mine,    most  common.     Square-sets  are  also  em- 

Nev*  ployed,  but  owing  to  the  cost  of  suitable 

2.  Gold  and  Silver. 

3.  Veins.  timber,  that  method  of  support  is  resorted 

4.  Width  8  to  10  ft.  ,  .   ,  ~     . 

to  only  in  special  cases.  Owing  to  the 
value  of  the  ores,  which  ranges  from  $12.00  to  $50.00  a  ton, 
it  is  desirable  if  possible  to  remove  the  entire  mass  of  the 
vein-filling  and  often  a  part  of  the  wall  rock.  The  total 
extraction  of  the  ore  is  then  the  ultimate  aim  of  the  mining 
operations,  which  is  readily  accomplished  by  the  method 
employed,  being  overhand  stoping  by  the  use  of  stulls. 

The  ore  formation  consists  of  a  broad  belt  of  fissure  veins 
often  occurring  close  together.  The  deposits  occur  in  ande- 
site  either  as  fissure  or  contact  veins,  and  but  few  of  them 
reach  the  surface.  A  peculiar  feature  observed  in  working 
some  of  the  larger  veins  is  that  their  course  as  followed  on 
the  dip  is  broken  by  flats  and  pitches,  resembling  to  a  marked 
degree  a  huge  flight  of  stairs,  which  is  due  to  faulting. 

The  veins  are  opened  and  developed  by  vertical  shafts  and 
cross-cuts,  which  divide  the  deposits  into  lifts  lying  between 
levels  spaced  about  ioo  ft.  apart.  In  the  Tonopah  Mine 
stopes  are  carried  up  the  full  width  of  the  vein,  the  walls 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS  101 

being  supported  by  stulls.  At  a  height  of  8  to  9  ft.  above 
the  sill-floor  of  the  stope  a  row  of  stulls  is  placed  in  a  hori- 
zontal position  and  wedged  fast  between  the  walls.  In 
order  to  properly  support  the  horizontal  stulls  two  or  more 
posts,  depending  upon  the  width  of  the  vein,  are  set  up 
under  each  stull  and  upon  similarly  placed  sills  on  the  stope- 
floor.  When  lagging  has  been  placed  upon  the  horizontal 
stulls,  the  so-called  l  stull-floors '  are  formed.  (See  Fig.  30.) 
One  or  more  rows  of  ore  chutes  are  built  in  between  the 
stulls,  being  placed  on  both  sides  of  the  vein  or  on  one  side 
only,  the  number  and  arrangement  depending  upon  the 
width  of  the  vein.  A  chute  placed  at  one  side  of  the  stull- 
floor,  in  wide  veins,  necessitates  too  much  shoveling  of  ore 
in  finally  clearing  the  stopes.  Stoping  is  continued  upward, 
the  walls  being  supported  by  other  rows  of  stulls  spaced  from 
6  to  15  ft.  apart  vertically,  depending  upon  conditions  of 
the  wall  rock.  These  stulls  also  serve  as  supports  for  lagging 
or  scaffoldings  upon  which  the  miners  stand  and  mount  their 
drills.  Owing  to  the  small  size  of  the  timbers  used,  which 
seldom  exceeds  8  in.,  and  the  increased  width  of  stopes 
in  many  places,  it  is  often  found  necessary  to  place  props  or 
struts  between  the  stulls  to  prevent  their  buckling  and 
breaking.  All  stulls  are  provided  with  blocking  called 
'  stullheadings '  which  increase  the  bearing  of  the  stulls  and 
at  the  same  time  afford  a  better  footing  for  them. 

A  stope  having  reached  the  level  above  and  been  broken 
through  into  it,  props  are  carefully  set  between  the  stope- 
sills  and  the  last  placed  stulls  in  the  stope  below,  thus  pro- 
viding a  fairly  strong  support  for  the  level  timbers  above. 


IO2 


ORE  MINING  METHODS 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS          103 

No  stope  should  be  worked  out  and  connected  with  a  level 
above  until  the  upper  level  has  been  worked  and  the  ore 
drawn  off,  or  the  ore  should  be  drawn  off  practically  as  fast 
as  broken  in  order  that  undue  weight  may  not  be  thrown 
upon  the  stulls  supporting  the  levels.  (See  Fig.  30.) 

At  the  natter  portions  of  the  veins  considerable  difficulty 
is  often  experienced  in  setting  the  stulls,  especially  the 
horizontal  ones,  and  consequently  square-set  timbering  is 
largely  employed  at  such  places;  greater  strength  is  also 
obtained. 

Filling  is  occasionally  used  in  connection  with  square- 
sets,  but  probably  to  a  greater  extent  with  stulls,  the  empty 
stopes  being  run  full  of  waste  rock,  which  can  be  trans- 
ferred from  stope  to  stope  as  the  upper  levels  are  exhausted. 

The  method  of  working  with  horizontal  and  inclined 
stulls  as  employed  in  the  Tonopah  mines  is  applicable  to 
narrow  and  moderately  wide  veins  of  high  dips  and  with 
fairly  strong  and  solid  walls.  While  it  might  be  employed 
in  working  low-grade  ores,  it  is  especially  suited  to  mod- 
erately high-grade  ores,  where  it  is  desirable  to  make  a 
high  percentage  extraction  of  ore. 

The  advantages  of  the  method  are: 

1.  The  complete  extraction  of  ore. 

2.  Use  of  relatively  small  timbers. 

3.  Ease  of  handling  ore. 

4.  Ready  access  to  the  stopes. 

5.  A  certain  amount  of  ore  may  be  held  in  the  stopes  as 
a  reserve. 

6.  Ventilation  is  good. 


104  ORE  MINING  METHODS 

The  disadvantages  of  the  method  are: 

1.  Use  of  considerable  timber,  which  is  expensive. 

2.  Confined  to  high  dips. 

3.  Lack  of  stability  of  workings  when  stopes  are  con- 
nected. 

4.  Stoppage  of  ore  chutes,  necessitating  blasting  out  the 
ore,  thus  injuring  chutes. 

5.  Little  opportunity  to  sort  and  stow  waste  rock. 

Stull-level  Method 

The  application  of  overhand  or  back  stoping  to  veins  of 

variable  width  is  shown  to  advantage  in  the  Combination 

i  Combination          Mine,  Goldfield,  Nevada.1    The  lodes  of 

Mine,  Goidfieid,    ^  Qoldfield  district  consist  of  shattered 

2.  Gold  and  Silver,     and  fissured  zones  of  silicification.     In  the 

3.  Veins  or  Zones.  . 

4.  Average  thickness    Combination  Mine  the  vein-filling  as  well 

as  the  country  rock  is  altered  dacite.  Oc- 
casionally the  silicified  zones  extend  into  the  walls,  making 
the  width  of  the  workable  deposit  rather  indeterminate. 
The  width  of  the  silicified  zones  usually  does  not  exceed  50 
ft.,  while  in  the  majority  of  cases  20  ft.  is  a  fair  average.  As 
a  usual  thing  the  ground  is  easy  to  support  and  wide  stopes 
are  often  worked  without  fear  of  collapse. 

Referring  to  the  section,  Fig.  31,  it  is  seen  that  the  first 
level  was  formed  at  a  depth  of  80  ft.,  two  passages  being 
driven  in  the  deposit  to  the  limits  of  the  ore-shoot,  one  on 
either  side  of  the  lode.  By  cutting-out  stoping,  both  of  the 

1  The  Combination  Mine,  by  Edgar  A.  Collins.  Mining  &  Scientific 
Press,  vol.  95,  p.  435. 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS 


105 


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io6  ORE  MINING  METHODS 

passages  were  increased  in  height  and  width  until  they  ran 
together  in  the  center  of  the  lode  and  at  the  same  time 
were  extended  to  the  walls  of  the  lode.  As  soon  as  sufficient 
height  of  stope  was  secured  to  permit  the  running  of  cars, 
stulls  and  lagging  were  placed.  Subsequent  work  filled  the 
stope  with  broken  ore  which  was  drawn  off  as  desired  by 
chutes  spaced  every  20  ft.  along  the  levels.  The  width  of 
the  stope  was  increased  ultimately  to  50  ft.  at  one  or  more 
points,  but  stood  without  support  by  carefully  arching  the 
back.  The  combined  s topes  were  raised  to  within  about 
15  ft.  of  the  surface,  when  raises  were  put  up  breaking 
through,  the  remainder  of  the  arch  being  cut  out  by  under- 
hand work. 

In  the  meantime  a  second  level  was  driven,  as  shown,  at 
the  i3o-ft.  level,  which  was,  however,  carried  the  full  width 
of  the  lode,  being  narrower  at  this  point  than  above,  and  was 
stulled  and  lagged  with  timbers  of  suitable  size.  The 
second  stope  was  raised  to  within  about  6  feet  of  the  8o-ft. 
level,  and  raises  were  driven  connecting  the  levels  above 
with  the  stope  below.  All  handling  of  ore  on  the  first 
level  was  then  abandoned  and  the  ore  from  the  upper  stope 
was  drawn  off  through  the  raises  connecting  the  stopes. 
As  the  ore  was  drawn  from  the  upper  stope  the  pillars  above 
the  levels  were  exposed  and  were  attacked  and  stoped  out, 
at  the  same  time  any  ore  exposed  on  the  walls  of  the  open 
stope  was  broken  down  and  ultimately  loaded  into  cars  on 
the  i3o-ft.  level. 

The  third  level  was  formed  at  the  23o-ft.  point,  the 
ground  between  it  and  the  second  level  being  worked  by 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS  107 

intermediate  levels  spaced  50  ft.  apart,  especially  in  the 
weaker  ground,  as  in  the  sulphide  ores.  The  intermediate 
levels  are  strongly  timbered.  It  is  proposed  to  fill  the  stopes 
with  waste  after  the  ore  has  been  withdrawn. 

This  particular  method  of  mining  is  applicable  to  veins  of 
varying  widths  and  dips,  as  widths  of  20  to  50  ft.  and  dips 
of  30  to  90°  with  the  horizontal,  also  to  strong  and  mod- 
erately strong  ores  and  wall  rocks. 

The  advantages  of  this  method  are : 

1.  Little  timber  is  necessary. 

2.  The  ore  is  handled  with  little  labor. 

3.  By  opening  the  mine  to  the  surface  the  ore  in  the 
wall  rock  can  be  more  carefully  and  systematically  mined. 

4.  Ventilation  is  good. 

The  disadvantages  of  the  method  are: 

1.  Short  distance  between  levels  and  expense  of  forming 
a  number  of  levels,  especially  sub  or  intermediate  levels. 

2.  A  possible  loss  of  high-grade  ore  by  breakage  in  draw- 
ing from  one  stope  to  another. 

3.  The  accumulation  of  water  in  workings  due  to  open- 
cuts. 

4.  The  necessity  of  using  long  stulls  and  consequently 
large  ones  on  those  levels  where  the  lode  is  wide. 


io8  ORE  MINING  METHODS 

The  Stull-set  Method 

The  employment  of  stulls  in  veins  varying  in  width  from 
15  ft.  and  over  is  shown  to  good  advantage  in  the  lead- 

silver  mineS  °f  the  Coeur  ^'Alene  district1 


1.  The  Hecla  Mine, 

Burke,  Idaho.     w^ere  the  system  has  its  widest  application. 

2.  Lead  and  Silver. 

3.  Veins.  The  veins  occur  in  slates  and  quartzites 

4.  Width  8  to  35  ft.  11  .-,        1-1  -\          r  j  •       -L    • 

and  have  rather  high  angles  of  dip,  being 
not  far  from  70°  with  the  horizontal.  They  range  from  8  to 
15  even  up  to  35  ft.  in  width,  the  walls  often  being  inde- 
terminate and  disintegrating  badly  on  exposure  to  the  air. 

The  ore  is  broken  by  overhand  stoping,  locally  known  as 
'back  stoping/  the  walls  and  back  of  ore  being  supported 
by  'stull-sets'  and  filling.  (See  Fig.  32.) 

The  levels  are  usually  driven  250  to  300  ft.  apart,  the 
stopes  being  opened  directly  off  the  levels  and  usually  to  the 
full  width  of  the  vein.  The  supporting  stull-sets  are  built 
up  from  the  levels  and  are  kept  open  for  the  first  two  floors 
for  convenience  in  handling  timber,  after  which  they  are 
usually  filled  with  barren  material,  sorted  from  the  vein 
during  mining.  The  height  of  the  stull  posts  varies  in  the 
different  mines  from  6  ft.  to  8  ft.  3  in.,  making  the  distance 
between  floors  approximately  9  and  10  ft.  respectively. 
The  size  of  the  stulls  and  posts  ranges  from  10  to  16  in.  in 
diameter.  Occasionally  the  stull-sets  are  reenforced  by 
other  sets  placed  below  them,  which  is  usually  done  on  the 
second  floor.  The  posts  of  the  stull-sets  are  usually  placed 

1  Mining  Methods  in  the  Coeur  d'Alene  District,  Idaho,  by  Robt.  N.  Bell. 
Mining  Magazine  (American),  vol.  13,  p.  306;  Fifteenth  Annl.  Rept.  of  the 
Mining  Industry  of  Idaho,  by  Robt.  N.  Bell.  pp.  90  and  92,  1913. 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS  109 


FIG.  32. —  Application  of  Stull-Sets  to  the  Mining  of  Medium-sized  Veins. 


no  ORE  MINING  METHODS 

from  4  to  6  ft.  apart  and  from  18  in.  to  3  ft.  from  the  walls 
in  order  to  allow  for  cutting  off  the  ends  of  the  stulls  when 
they  begin  to  break  and  splinter  as  the  weight  of  the  walls 
comes  more  upon  them.  On  cutting  away  the  broken  ends 
of  the  stulls  the  old  blocking  or  '  head  boards '  are  removed, 
the  walls  smoothed  up  and  new  boards  placed,  the  whole 


FIG.  33.  — Plan  of  Second  'Floor  of  Stull-Set  Method. 
(Modeled  after  Sketch  by  Robert  N.  Bell.) 


being  wedged  fast  again.     The  stull-sets  are  spaced  from  5 
to  8  ft.  apart  along  the  levels  or  stopes.     (See  Fig.  33.) 

Above  the  second  floor  and  on  top  of  the  stulls  long  tim- 
bers are  placed  running  longitudinally  with  the  stope,  upon 
which  in  turn  are  laid  other  timbers  but  extending  directly 
across  the  vein.  These  latter  timbers  or  sills  are  placed 
about  4  ft.  apart,  and  when  covered  with  lagging  form  the 
floor  upon  which  the  waste-filling  is  placed.  The  lagging  is 


MINING   IN  VEINS  AND  BEDDED  DEPOSITS          in 

sawed  timber  3  by  12  in.  and  of  suitable  length  to  reach 
at  least  from  the  center  of  one  sill  to  another.     (See  Fig.  34.) 
An  open  space  is  maintained  around  the  ore  chutes,  man- 
ways  and  timber  slides,  beginning  with  the  second  floor  of  each 


FIG.  34.  —  Vertical  Section  through  Vein  Showing  Method  of  Placing  Stull-Sets. 
(Modeled  after  Sketch  by  Robert  N.  Bell.) 

level,  by  boarding  off  a  portion  of  the  stope,  which  open  space 
is  maintained  to  the  working  face  of  the  stope.  In  narrow 
veins  theboarded-up  partitions  extend  from  wall  to  wall,  while 
in  wider  veins  a  relatively  large  space  is  fenced  in.  (See  Fig.  3  5). 


112 


ORE  MINING  METHODS 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS          113 

Room  is  thus  provided  for  handling  ore  and  timber  and  for 
the  passage  of  men  as  the  stope  increases  in  height.  The 
remaining  portion  of  the  vein  is  filled  in  with  waste  and  is 
commonly  known  as  the  '  corral. '  (See  Figs.  33  and  35.) 

The  waste-filling  is  carried  to  within  two  sets  of  stalls  or 
floors  of  the  face  or  back  of  the  stope,  the  floors  upon  which 
the  stoping  drills  are  mounted  consisting  of  lagging  placed 
upon  the  stulls.  This  lagging  is  removed  prior  to  placing 
the  filling,  and  is  used  over  and  over  again  as  the  stopes  in- 
crease in  height.  Temporary  supports  as  posts  are  placed 
between  the  stulls  and  back  of  stope  and  are  specially 
needed  in  wide  veins  and  heavy  ground. 

The  ore  as  broken  falls  upon  the  lagging  of  plank,  from 
which  it  is  shoveled  into  chutes  after  being  sorted;  the  waste 
is  then  stowed  in  the  corrals  below. 

The  stull-set  method  of  mining  is  applicable  to  highly 
inclined  deposits  varying  in  width  from  10  to  35  and  40  ft. 
It  is  possible  to  work  deposits  the  walls  of  which  are  heavy 
and  weak,  but  it  is  most  applicable  to  strong  walls  and  ores 
that  will  stand  well. 

The  advantages  of  the  stull-set  method  are: 

1.  The  comparative  ease  of  handling  and  placing  timbers, 
the  number  of  pieces  being  less  than  employed  with  the 
square-set  method. 

2.  The  possibility  of  easing  up  the  timbers  and  repairing 
broken  stulls.     Badly  broken  wall  rock  can  be  removed  and 
the  support  renewed  with  little  trouble, 

3.  Increased  height  of  stope  that  can  be  worked  even  in 
bad  ground. 


H4  ORE  MINING  METHODS 

4.  Convenience  of  sorting  ore  and  storing  waste  with 
little  handling. 

5.  Safety  to  men,  numerous  means  of  escape  from  stopes 
being  provided. 

6.  Ventilation  in  stopes  is  good. 

7.  Large  percentage  extraction  is  possible. 
The  disadvantages  of  the  stull-set  method  are: 

1.  Considerable  timber  is  used  and  especially  large  sizes 
which  are  difficult  to  handle. 

2.  Method  is  limited  to  steep  dips  and  consequently  the 
stopes  must  be  carried  nearly  vertically. 

3.  The  difficulty  experienced  in  maintaining  the  large 
areas  of  open  stopes  both  horizontally  and  vertically. 

MINING   MINERAL  VEINS  BY  THE   USE  or   SQUARE-SETS 

Horizontal  and  Inclined  Floor  Methods 
Square-set  mining  is  extensively  used  in  the  Coeur  d'Alene 
lead-silver  district,  although  in  the  narrow  portions  of  the 
deposits  simple  posts  and  stulls  are  often  employed,  espe- 
cially if  the  roof  is  strong  and  firm.  The  application  of 
square-sets  to  the  wider  portions  of  the  deposits,  which 
range  in  width  from  5  to  50  ft.,  varies  both  with  the  dips 
and  the  character  of  the  ore.  The  older  method  consists 

1.  The  Bunker  Hill-  in  overhand  stoping  the  deposit  in  hori- 

SuUivan    Mine, 

Wardner, Idaho,  zontal  floors,  the  stopes  being  filled  with 

2.  Lead  and   Silver.  ... 

3.  Veins.  square-sets   as   rapidly   as   space   is   pro- 

4.  Width  5  to  50  ft.  vjded  for  them.     The  more  recent  method 
differs  mainly  from  the  earlier  method  in  that  the  working 
face  is  carried  normal  to  the  foot-wall  or  as  nearly  so  as 


MINING  IN   VEINS  AND  BEDDED  DEPOSITS          115 

possible.  The  object  of  this  method  of  procedure  is  to 
transfer  the  weight  of  the  ore  largely  from  the  square-sets 
to  the  foot-wall. 

The  method  of  stoping  in  horizontal  floors  represents  ex- 
tensive practice  in  the  working  of  metalliferous  mines  in  all 
parts  of  the  world,  being  applicable  to  both  fairly  steep  and 
slightly  dipping  veins.  In  the  Cceur  d'Alene  district  it  has 
been  successfully  employed  in  lodes  dipping  from  35  to  70°. 
The  square-sets  are  usually  9  by  5  by  6  ft.,  i.e.,  the  posts  are 
9  ft.,  the  girts  5  ft.  and  the  caps  6  ft.  long.  (See  Fig.  36.) 

The  veins  are  usually  opened  by  tunnels,  although  a  few 
shafts  are  employed  where  conditions  permit;  however, 
regardless  of  how  opened,  the  actual  development  of  the 
orebodies  is  by  shafts,  either  extending  from  the  surface 
or  beginning  underground  as  winzes,  the  levels  being  driven 
from  them  to  the  deposit.  In  the  deposits,  especially  in  the 
wider  veins,  two  passages  are  usually  maintained  through 
the  timbered  stopes,  which  are  mainly  for  the  convenience 
of  handling  the  ore.  Two  sets  of  timbered  chutes  and 
an  occasional  manway  extend  from  the  open  stope  above 
to  the  passages  below,  thus  maintaining  as  nearly  as  pos- 
sible equal  convenience  in  handling  ore  across  the  vein. 
The  stopes  are  kept  filled  to  within  about  one  set  of  the  top, 
thus  providing  ample  support  to  the  walls  and  roof  as  well 
as  space  to  work  in  and  protection  to  the  miners. 

As  previously  indicated,  where  the  ore  is  weak  and  heavy, 
throwing  much  weight  upon  the  square-sets,  the  more 
recent  method  of  carrying  the  working  face  normal  to  the 
foot-wall  is  now  being  successfully  employed. 


n6 


ORE  MINING  METHODS 


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S 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS  117 

The  development  work  is  similar  in  both  methods  of 
working,  and  while  two  haulage  ways  may  be  maintained 
through  the  timbered  stopes,  the  same  advantage  may  be 
secured,  so  far  as  handling  ore  in  the  stopes  is  concerned,  by 
employing  branched  chutes.  The  branch -chutes  may  be 
attached  to  the  main  chutes  at  any  desired  point  before 
the  filling  is  placed,  the  slope  of  the  chute  being  carefully 
maintained  in  order  to  insure  positive  and  rapid  transfer- 
ence of  ore  from  the  face  to  the  loading  chute  below.  Ore 
chutes  are  placed  from  15  to  30  ft.  apart,  while  the  man- 
ways  are  50  ft.  apart. 

In  stoping,  the  face  is  attacked  next  to  the  hanging-wall 
and  the  excavation  is  supported  by  placing  sets  as  soon  as 
room  is  made  for  them.  The  work  of  cutting  out  the  in- 
clined slice  then  proceeds  downward  until  the  foot-wall  is 
reached,  the  placing  of  sets  following  the  excavation.  This 
operation  is  repeated  until  the  desired  height  of  stope  is 
reached,  when  work  on  a  new  level  is  begun.  (See  Fig.  37.) 
Filling  is  drawn  from  old  stopes  and  from  drifts  driven  into 
the  hanging-walls  and  is  usually  kept  within  one  set  of  the 
face. 

The  application  of  square-sets  in  mining  as  a  means  of 
support  has  previously  been  pointed  out,  but  the  latter  of 
the  two  methods  described  above  illustrates  how  their 
usefulness  may  be  extended  under  particularly  difficult 
conditions. 


n8 


ORE  MINING  METHODS 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS          119 

MINING  MINERAL  VEINS  BY  THE  USE  or  FILLING 

Rill  Sloping 

The  application  of  filling  to  the  working  of  the  gold  mines 
of  Zaruma,  Ecuador,1  is  somewhat  unique  in  that  instead  of 
placing  the  filling  in  horizontal  floors  it  is  run  in  from 
above  and  stands  at  about  its  natural  " angle  of  repose." 
The  vein-matter  is  quartz  bearing  con- 

..       ,,  .  .         '          f.      ,         ,.  .      1.   Zaruma,  Ecuador 

siderable    quantities    of    finely    dissemi-  S.A. 

nated    pyrites,    and    bunches    of    galena   *'  ^ Ore* 
and    blende    next    to    the    hanging- wall.    4.  Maximum  width 

26ft. 

The  wall  rock  is  diorite.  The  vein  is 
faulted  by  an  extensive  fault-plane  which  lies  within  the 
vein  and  on  the  contact  of  foot-wall  and  vein-matter. 
Owing  to  the  extensiveness  of  the  movement,  a  very  heavy 
gouge  occurs  which  ranges  between  3  and  4  ft.  in  thickness 
and  is  extremely  weak  and  treacherous.  The  value  of  the 
ore  is  between  $4  and  $15  per  ton. 

In  developing  the  orebody  the  levels  are  run  in  the  foot- 
wall  at  a  distance  of  some  20  ft.  from  the  vein,  from  which 
cross-cuts  are  driven  every  65  ft.,  connecting  the  levels 
with  the  deposit.  From  the  various  points  of  attack  pro- 
vided by  the  cross-cuts  entering  the  orebody  stoping  is 
begun,  being  carried  the  full  width  of  the  vein  and  to  a 
height  of  about  8  ft.  (See  Fig.  38.) 

Connection  is  made  between  the  levels  and  the  surface 
by  means  of  a  number  of  raises  along  the  foot-wall  through 
which  waste  rock  is  introduced  into  the  stopes.  Begin- 

1  Notes  on  the  Gold-Mines  of  Zaruma,  Ecuador,  by  J.  Ralph  Finlay. 
Trans.  Am.  Inst.  Mining  Engrs.,  vol.  30,  p.  248. 


120 


ORE  MINING  METHODS 


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ning  at  the  raises  the  ore  is  cut  out  by  overhand  stoping, 
the  ore  being  cleared  away  as  rapidly  as  possible  and  hauled 
through  the  cross-cuts  and  levels  to  the  main  shaft.  When 
the  stopes  have  been  carried  as  high  as  is  considered  safe, 
filling  is  thrown  down  the  raises  until  the  stopes  are  nearly 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS          121 

filled;  the  work  of  stoping  is  then  resumed,  but  to  prevent 
the  mixing  of  ore  and  waste  rock,  slabs  of  wood  are  placed 
upon  the  sloping  sides  of  the  filling.  This  operation  is 
repeated,  each  slice  being  carried  as  far  as  is  considered 
safe  and  then  filling  is  run  in  to  support  the  walls  and  bring 
the  footing  for  the  drills  sufficiently  close  to  the  working 
face.  Further  temporary  supports,  as  posts,  may  be  set 
up  between  the  face  and  the  filling  as  occasion  demands. 
The  filling  run  in  from  above  distributes  itself  evenly  in  the 
stopes  without  extra  handling,  and  as  the  work  of  stoping  is 
carried  on  from  the  slope  of  the  filling  the  stope  face  must 
of  necessity  be  maintained  parallel  with  the  slope  of  the 
filling,  which  is  practically  that  of  the  angle  of  repose  of  the 
waste  rock,  but  slightly  less  owing  to  the  miners  working 
upon  the  filling. 

In  the  course  of  time  the  various  stopes  run  together  and 
at  points  midway  between  the  raises,  or  at  the  intermediate 
cross-cuts.  At  these  points  cribbed  chutes  are  begun  and 
built  upward  as  the  work  of  stoping  and  filling  proceeds. 
Cribbed  manways  are  maintained  through  the  center  of  the 
stopes  to  provide  means  of  ingress  and  egress  to  and  from 
the  stopes.  (See  Figs.  38  and  39.) 

The  method  of  filling  employed  at  the  Zaruma  mines  is 
applicable  to  moderately  wide  deposits  of  solid  and  firm  ore 
but  not  extra  strong  walls.  The  method  is  usually  desig- 
nated as  'rill  stoping.' 

The  advantages  of  the  method  are: 

1.  Little  timber  is  required. 

2.  Levels  may  be  placed  a  considerable  distance  apart. 


122 


ORE  MINING  METHODS 


3.  There  is  a  minimum  amount  of  handling  of  ore  and 
waste-filling. 

4.  Filling  can  be  carried  close  to  the  face,  as  it  does  not 
have  to  be  distributed. 

5.  Ventilation  is  good. 

The  disadvantages  of  the  method  are: 

1 .  The  inconvenience  of  working  on  a  sloping  bank  of  filling. 

2.  Loss  of  ore  by  mixing  with  waste. 

3.  Stoppage  of  all  work  in  a  stope  while  running  in  filling. 

4.  Little  opportunity  to  sort  ore  in  stopes. 


FIG.  39.  —  Rill-Stoping  Showing  the  Use  of  Planks  on  Sloping  Banks  of  Waste- 
Filling,  also  Methods  of  Entering  Stopes  and  Disposing  of  Ore. 

Back-filling  Method 

A  variety  of  methods  of  mining  is  to  be  found  in  use 
in  the  copper  mines  of  Butte,  Montana,  some  of  the  more 
1.  St.  Lawrence  Mine,  important  of  which  are :  the  use  of  stulls 
and  lagging,  with  or  without  filling; 
square-set  timbering,  with  or  without 
filling,  and  a  method  of  filling  without 
timbering,  known  as  ' back-filling.' 


Butte,  Mont. 
It.   Copper  Ore. 

3.  Vein. 

4.  8  to  50  ft.  in  width. 


MINING  IN  VEINS  AND   BEDDED   DEPOSITS  123 

The  width  of  the  veins  worked  by  this  method  varies  from 
8  to  50  ft.  and  they  dip  at  fairly  high  angles,  although  that 
is  not  a  requisite.  The  country  rock  is  granite,  which  is 
usually  fairly  strong  and  solid,  standing  well.  The  vein- 
matter  is  quartz  with  pyrite  and  copper  minerals. 

The  deposits  are  developed  by  vertical  shafts  from  which 
cross-cuts  are  driven  to  the  veins  at  intervals  of  200  ft., 
levels  being  run  in  the  veins.  Stopes  may  be  opened  directly 
off  the  levels,  or  pillars  may  be  left  immediately  above  the 
levels;  in  the  former  case  the  filling  introduced  into  the 
stopes  to  support  the  walls  is  held  in  position  by  stulls  set 
along  the  levels,  while  in  the  latter  case  a  much  more  durable 
and  satisfactory  support  for  the  filling  is  provided  by  the 
pillars.  In  either  case  the  work  of  breaking  down  the  ore  is 
done  by  longwall  stoping.  (See  Fig.  40.)  Preparatory  to 
stoping  and  before  the  stopes  have  been  more  than  opened, 
waste  chutes  are  formed  in  the  foot-wall  connecting  both 
levels  and  stopes  and  are  spaced  80  to  100  ft.  apart  along 
the  vein.  Ore  chutes  and  manways,  built  up  from  the 
levels,  are  carried  upward  along  the  foot- wall  as  the  stopes 
increase  in  height,  being  strongly  timbered.  The  ore  chutes 
are  usually  placed  at  25  ft.  intervals,  while  the  manways  are 
100  to  125  ft.  apart.  It  is  customary  to  build  two-com- 
partment passages,  an  ore  chute  and  a  man  way  when  the 
two  come  together,  which  saves  time  and  expense. 

Beginning  at  a  raise  or  winze  cut  in  the  vein,  stopes  are 
worked  laterally  from  it,  being  carried  from  12  to  14  ft. 
high  and  the  full  width  of  the  vein.  As  rapidly  as  the 
broken  ore  can  be  cleared  from  the  stope  by  shoveling  it 


124 


ORE  MINING  METHODS 


FIG.  40. —  Elevation  and  Plan  of  Stopes.     Back-filling  Method. 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS  125 

into  the  ore  chutes,  waste  is  run  in,  filling  the  stope  to  a 
depth  of  about  8  ft.,  being  distributed  by  a  limited  amount 
of  shoveling.  Distribution  of  waste  is  done  largely  by  cars 
running  between  waste  chutes.  The  ore  chutes  are  tim- 
bered up  and  kept  above  the  level  of  the  filling.  A  space 
of  4  to  6  ft.  is  maintained  between  the  filling  and  the  back 
of  the  stope,  which  provides  room  for  handling  the  waste  in 
cars.  As  the  filling  is  carried  on  back  of  the  working  face 
of  the  stope  this  particular  method  of  handling  it  is  known 
as  'back-filling/  and  when  employed  in  a  mine  the  method 
of  mining  is  commonly  spoken  of  a  the  back-filling  method. 
Subsequent  stoping  is  carried  on  in  a  manner  similar  to  that 
of  the  initial  work,  the  stopes  being  from  12  to  14  ft.  high, 
and  the  successive  layers  of  filling  placed  are  8  ft.  thick. 
By  this  arrangement  the  stopes  where  work  is  being  done  are 
12  to  14  ft.  high,  while  the  space  between  filling  and  stope- 
back  is  maintained  at  a  fairly  uniform  height  of  4  to  6  ft. 

The  back-filling  method  is  usually  not  employed  except 
in  strong  or  moderately  firm  ground,  but  occasionally  ground 
is  worked  that  is  so  weak  that  props  must  be  used.  Usually 
no  attempt  is  made  to  draw  the  props  prior  to  blasting,  but 
they  are  pulled  out  of  the  broken  ore  as  it  is  shoveled  up. 
Comparatively  few  of  the  props  are  reused  as  supports  for 
the  back,  but  are  employed  in  building  chutes.  In  order  to 
prevent  loss  of  ore  from  mixing  with  the  waste-filling  during 
blasting  a  platform  or  mat  of  plank  is  placed  on  the  filling.1 

1  It  is  practically  impossible,  however,  to  prevent  a  certain  amount  of 
waste  mixing  with  the  ore  during  mining,  which  lowers  the  value  of  the 
ore  by  dilution  although  the  tonnage  is  increased.  The  increase  has  been 
estimated  at  between  2  to  10  per  cent. 


126  ORE  MINING  METHODS 

Planks  or  'floor-boards'  for  this  purpose  are  2  by  8  to  12 
in.  and  are  cut  in  8-ft.  lengths.  Shoveling  is  materially 
facilitated  by  the  use  of  such  platforms,  which  are  advanced 
with  the  s toping  face.  That  there  may  not  be  an  undue 
amount  of  shoveling  of  waste,  the  tracks  upon  which  the 
cars  carrying  the  filling  operate  are  frequently  shifted  from 
one  wall  to  the  other,  the  filling  being  run  in  to  place  rather 
than  shoveled.  (See  Fig.  41.) 

A  combination  of  rill  stoping  and  back-filling  may  be 
employed,  which  while  it  facilitates  the  placing  of  waste 
renders  the  sorting  and  handling  of  ore  more  difficult.  (See 
the  Dry- Wall  Method,  Fig.  43.) 

Stopes  may  be  completely  worked  out  by  this  method,  but 
it  is  the  usual  practice  to  leave  an  arch  pillar  of  12  to  16  ft.  in 
thickness  between  the  stopes  and  the  levels.  (See  Fig.  40.) 

The  back-filling  method  is  applicable  to  high  and  moder- 
ately high  dipping  veins.  The  wall  rock  and  ore  should  be 
fairly  strong  and  practically  self-supporting,  although  the 
use  of  props  is  common. 

The  advantages  of  the  method  are: 

1.  Under  favorable  conditions  little  or  no  timber  is  re- 
quired for  support. 

2.  Levels  are  far  apart,  reducing  the  amount  of  develop- 
ment work. 

3.  The  working  face  is  always  close  enough  for  thorough 
inspection,  thus  reducing  the  danger  of  accidents. 

4.  Large  outputs  are  possible. 

5.  Ore  can  be  sorted  and  waste  stowed  in  stopes. 

6.  Ventilation  is  good. 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS  127 


FIG.  41.  — Vertical  Section  through  Lode  Showing  Application  of  Back-Filling 
Method.  Chute  in  the  foot-wall  may  or  may  not  be  timbered,  but  should  be 
timbered  when  manways  are  combined  with  ore  chutes. 


128  ORE  MINING  METHODS 

The  disadvantages  of  the  method  are: 

1 .  Applicable  only  to  veins  having  strong  or  fairly  strong 
walls  and  ore. 

2.  Difficulty  and  expense  of  forming  waste  chutes. 

3.  Loss  of  ore  remaining  in  pillars. 

4.  Considerable  handling  of  ore  and  waste-filling. 

The  Dry-Wall  Method 

The  method  of  mining  employed  in  the  copper  mines  of 
the  Lake  Superior  region  is  overhand  stoping  with  slight 
modifications  in  handling  ore  due  to  varying  inclinations  of 
lodes.     The  dip  of  the  lodes  ranges  from  35  to  70°  in  the 
various  mines.     In  those  lodes  where  the  steeper  dips  pre- 
vail and  where   the  weight   of   the  walls  is   consequently 
less,  as  in  the  mines  of  the  Copper  Range   Consolidated, 
1   Baltic   and  Tri-    a   comParativery  new  method  of  mining 
Mines  *  Mich-   ^as  recentry  been  adopted,  which  is  vari- 
lgan-  ously    designated   as    the     'dry- wall'     or 

2.  Copper  Ore. 

3.  Vein.  the   'rock-wall'    and   again    simply    as    a 

4.  Width 24  to  36  ft.      <rn-  , 

filling  system. 

Copper  occurs  in  the  native  state  in  the  Lake  Superior 
copper  region,  being  found  in  both  sedimentary  and  inter- 
stratified  igneous  rocks.  The  copper  constitutes  a  cement 
which  surrounds  and  binds  together  the  pebbles  and  boulders 
of  porphyry  conglomerate,  or  fills  the  amygdules  especially 
in  the  upper  portions  of  the  interbedded  massive  rocks. 
In  the  Quincy,  Franklin  and  Altantic  mines  the  lodes  are 
amygdaloidal,  i.e.,  are  strongly  altered  diabase,  parts  of 
which  are  known  as  ash-beds. 


MINING  IN  VEINS  AND  BEDDED   DEPOSITS  129 

Stations  are  established  in  the  shafts  every  100  to  125 
ft.  along  the  lodes  from  which  levels  are  driven  8  ft.  high 
and  the  width  of  the  lode  wide.  The  level  drifts  are  en- 
larged by  cutting-out  stoping,  and  from  the  rock  broken 
down  the  larger  pieces  of  waste  are  employed  in  building 
the  pack  or  so-called  dry-walls  or  rock-walls,  which  are 
8  ft.  high  and  8  to  9  ft.  apart.  Occasionally  sections  of  logs 


FIG.  42. — Passage  Formed  on  Levels  by  'Rock-Walls,'  Showing  Use  of  Waste 
Rock  and  Logs  in  Their  Construction,  and  the  'Wall-Pieces'  and  Lagging 
Placed  on  Top  of  the  Walls.  (Modeled  after  Sketch  in  Eng.  and  Mining  Jour., 
vol.  97,  p.  949.) 

are  built  into  the  walls  and  strengthen  them  by  binding 
the  rocks  together.  (See  Fig.  42.)  On  these  walls  tim- 
bers are  placed  which  reach  from  wall  to  wall,  upon  which 
in  turn  is  laid  a  lagging  of  plank  or  poles.  The  timbers  are 
called  ' wall-pieces'  and  vary  in  size  from  18  to  24  in.,  being 
14  ft.  long.  As  the  work  of  stoping  proceeds  the  waste 
rock  sorted  out  is  stowed  between  the  pack-walls  and  the 
foot-  and  hanging-walls  until  these  spaces  are  full  and  is 


130  ORE  MINING  METHODS 

then  thrown  upon  the  lagging  covering  the  walled  passage. 
Mill-holes  are  begun  on  the  foot-wall  side  of  the  passage 
and  are  built  up  as  the  stope  increases  in  height.  (See 
Fig.  43.)  The  mill-holes  are  round,  5  ft.  in  diameter,  and 
when  completed  are  about  50  ft.  deep.  Owing  to  the 
steepness  and  width  of  the  lodes  it  is  necessary  to  mount 
the  drills  employed  in  cutting-out  stoping  between  the 
working  face  and  the  broken  ore  and  rock  below.  Pickers 
and  trammers  work  at  the  rear  of  the  bank  of  broken  rock, 
sorting  out  the  pay-rock  and  stowing  the  waste  in  the  stope, 
thus  leveling  the  rock  as  it  is  broken  down  in  advance. 
From  25  to  45  per  cent  of  the  lode-rock  is  waste  and  is  avail- 
able for  filling;  however,  if  there  is  not  a  sufficient  quantity 
to  fill  the  stopes,  the  foot-wall  may  be  broken  down  to  fur- 
nish more. 

Cutting-out  stoping  is  continued  up  to  within  about 
20  ft.  of  the  level  above,  when  it  is  stopped,  thus  leaving 
an  arch  pillar,  which  is  broken  at  more  or  less  regular  inter- 
vals by  openings  or  ' break-throughs.' 

At  the  Trimountain  Mine,  especially,  owing  to  the  irregu- 
larity of  the  foot- wall  and  fairly  uniform  hanging- wall,  it  is 
considered  advisable  to  carry  all  development  work  close  to 
the  latter. 

As  the  work  of  extracting  the  ore  proceeds  from  above 
downward,  an  upper  stope  is  first  worked  out,  and  when 
there  is  no  further  need  of  support  or  protection  of  the  level 
the  filling  is  drawn  off  into  the  next  lower  stope,  where  it 
serves  a  useful  purpose  in  assisting  in  stoping  out  the  arch 
pillars  by  providing  a  support  for  the  miners  in  drilling. 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS  131 


132  ORE  MINING  METHODS 

The  filling  is  drawn  off  by  making  openings  in  the  pack- walls 
of  the  filled  stopes  at  points  directly  over  break-throughs  in 
the  arch  pillars  of  the  stopes  to  be  filled.  The  stopes  are 
then  allowed  to  fill  as  full  as  the  size  of  the  break-throughs 
will  permit.  Drills  are  then  mounted  under  the  ends  of 
the  pillars,  adjacent  to  and  on  the  inclined  surface  of  the 
fills.  A  portion  of  the  pillars  about  10  ft.  in  width  and  from 
15  to  20  ft.  in  length  is  then  removed  as  in  cutting-out 
stoping.  The  drills  are  then  reversed  and  holes  are  drilled 
which  when  charged  and  fired  will  break  down  the  ends  of 
the  pillars,  thus  enlarging  the  openings  through  which  the 
filling  flows.  By  these  two  successive  operations  the  arch 
pillars  are  gradually  removed,  footing  for  the  miners  being 
provided  by  the  movement  of  the  filling  from  above,  thus 
maintaining  the  same  relative  position  with  respect  to  the 
pillars.  The  rock  as  broken  from  the  pillars  falls  upon 
the  surface  of  the  filling  and  is  carried  to  the  pickers  below 
by  its  downward  and  lateral  movement.  A  number  of 
break-throughs  may  be  opened  in  a  similar  manner  in  the 
same  stope,  thus  permitting  rapid  removal  of  the  arch  pillars 
and  the  filling  of  the  stopes.  Picking  of  pay-rock  and 
spreading  of  waste  are  carried  on  as  in  cutting-out 
stoping. 

The  method  is  applicable  to  moderately  wide  and  steeply 
dipping  lodes  from  which  considerable  waste  rock  can  be 
obtained  by  sorting  and  if  necessary  from  special  excava- 
tions. The  ore  and  walls  should  be  fairly  strong  and  firm, 
as  they  must  stand  temporarily  often  for  considerable  dis- 
tances without  support. 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS          133 

The  advantages  of  the  filling  method  described  above  are  : 

1.  Little  timber  is  required. 

2.  The  complete  extraction  of  ore  in  the  lode. 

3.  All  waste  rock  is  stowed  in  the  mine  with  little  handling. 

4.  A  fairly  clean  product  is  sent  to  the  surface. 

5.  Ease  of  stoping  and  reduced  cost  of  mining. 

6.  The  repeated  use  of  filling  for  support  of  workings. 

7.  Placing  of  levels  a  considerable  distance  apart. 
The  disadvantages  of  the  method  are: 

1.  Applicable  to  highly  inclined  lodes. 

2.  Cost  of  building  pack-  walls. 

3.  Considerable  handling  of  ore  in  stopes. 

4.  Collapse  of  upper  levels  on  withdrawal  of  filling  and 
danger  of  a  crush  starting  and  extending  to  lower  levels. 

5.  Loss  of  ore  by  mixing  with  waste  in  cutting-out  arch 
pillars. 

MINING  BEDDED  DEPOSITS  BY  CAVING 

Sub-drift  System 

The  sub-drift  system  of  mining  has  been  successfully 
employed  in  the  Mercur  and  Golden  Gate  mines  of  Mercur, 
Utah.1  The  ores  are  oxidized  and  base. 

1.   Mercur  and  Golden 

carrying   gold  and    occur    in   limestone         Gate  Mines,  Mer- 
and  shale  formations.     The  dip  of  the   2.  Gold  Ore. 

,     ,  j-  r          i  3.   Bedded  deposit. 

ledges  ranges  from  a  few  degrees  up  to   4   15  to  20  *ft 


25°,  necessitating  the  use  of  inclines  to          and  up. 
develop  the  orebodies,  which  are  often  driven  next  to  the 
roof  or  in  the  upper  part  of  the  mineralized  portion  of  the 

1  Mines  and  Mining  of  the  Consolidated  Mercur  Company,  by  Ray 
Hutchins  Allen.     Eng.  Mining  Jour.,  vol.  89,  p.  1273. 


134  ORE  MINING  METHODS 

ledge.  When  driven  at  the  bottom  of  the  orebody,  there 
is  probably  more  danger  of  the  passage  being  destroyed 
by  the  caving  of  ground  above.  (See  Fig.  44.) 

When  the  ledge  is  15  to  20  ft.  thick,  that  part  of  the 
deposit  from  the  hanging-wall  to  and  including  the  first  set 
of  longitudinal  drifts  on  the  respective  subs  would  represent 
the  ledge  worked,  the  incline  connecting  the  drifts.  With 
ledges  of  greater  thickness,  often  reaching  100  ft.,  the  whole 


'S  "*"/S 

iiMorni 


FIG.  44.  —  Transverse  Section  through  Deposit  Showing  Method  of  Developing 
Thick  Deposit.  A  thin  deposit  would  have  the  incline  near  the  top  or 
hanging  wall. 

section,  as  shown,  would  represent  the  conditions,  the  incline 
being  at  the  bottom  of  the  ledge.  The  system  of  working 
thin  ledges  is  quite  simple  and  can  be  described  to  advan- 
tage prior  to  taking  up  the  more  complicated  method  of 
working  the  thicker  ledges. 

An  incline  having  been  run  along  the  floor  of  the  deposit, 
1  sub-drifts'  are  driven  longitudinally  in  the  ledge,  from 
15  to  25  ft.  apart  and  to  the  limit  of  the  workable  deposit. 
(See  Figs.  44  and  45.)  Stoping  is  first  begun  on  the  sides 


MINING  IN  VEINS  AND   BEDDED  DEPOSITS  135 

of  'sub-drift'  No.  i,  supporting  posts  or  stulls  in  the  higher 
dips  being  placed  as  the  stope  widens.  After  the  pillars 
of  sub  No.  i  have  been  drawn  back  20  to  25  ft.  work  is 
begun  on  sub  No.  2  and  in  a  similar  manner  subs  Nos.  3  arid 
4  are  worked  in  order.  When  the  stope  faces  of  subs  Nos. 
i  and  2  have  been  connected,  one-half  of  the  pillars  between 
them  and  that  portion  between  sub  No.  i  and  the  caved 
ground  above  are  drawn  back  by  breast  stoping  or  '  side- 
swiping7  and  the  ore  in  the  roof  is  caved  by  knocking  out 
posts  and  blasting  the  back.  The  drifts  furnish  protec- 
tion for  the  men  when  caving  is  under  way.  In  a  similar 
manner  the  pillars  between  subs  Nos.  2  and  3  and  3  and  4, 
and  so  on,  as  rapidly  as  the  subs  are  driven,  may  be  drawn 
and  the  roof  caved.  Each  retreating  pillar  face  is  kept  from 
12  to  20  ft.  in  advance  of  the  adjacent  one  down  the  slope, 
thus  maintaining. conditions  most  suitable  to  pillar-drawing 
as  determined  by  experience  in  these  mines  and  similar 
work  in  coal  mining.  Under  the  most  favorable  conditions 
the  removal  of  drift  sets  and  posts  is  all  that  is  necessary  to 
start  the  back  caving.  The  miner  then  shovels  the  ore  into 
cars  and  trams  it  to  the  incline  or  in  the  upper  subs  to  chutes 
provided  at  intervals  of  about  50  ft.  (See  Figs.  44  and  45.) 
When  waste  begins  to  come  and  mix  with  the  ore  it  is 
evident  that  the  roof  formation  is  down,  and  the  miner 
prepares  for  another  cave  by  taking  out  the  supporting 
posts  next  to  the  face.  Under  no  condition  should  a  lower 
pillar  be  allowed  to  retreat  faster  than  an  upper,  as  a  cave 
would  be  almost  sure  to  take  place  in  the  upper  pillar,  losing 
ore  and  endangering  the  miners  working  in  the  sub  above. 


136 


ORE  MINING  METHODS 


In  thick  deposits  the  same  method  of  procedure  is  fol- 
lowed but  is  applied  to  a  series  of  inclined  benches  or 
layers  of  deposit,  about  15  ft.  thick,  superimposed  one  upon 


FIG.  45. — Longitudinal  Section  through  the  Sub-drifts  Showing  the  Incline  on 
the  Right,  also  Other  Passages  Driven  across  the  Deposit  from  the  Sub-drifts. 


the  other,  the  series  of  subs  in  the  respective  layers  or 
benches  being  connected  by  cross-cuts.  The  upper  portion 
of  the  deposit  is  carried  considerably  in  advance  of  the  lower- 
most bench,  each  bench  being  advanced  in  a  manner  and 


MINING  IN  VEINS  AND  BEDDED  DEPOSITS          137 

amount  similar  to  the  retreating  pillar  faces  in  the  separate 
benches  as  previously  described.  (See  Figs.  44  and  45.) 

Under  certain  conditions  of  deposit  and  roof  the  whole 
deposit  throughout  the  series  of  sub-drifts  may  be  caved  at 
one  and  the  same  operation  by  beginning  at  the  top  and 
starting  a  cave  in  each  sub.  The  whole  deposit  can  in  this 
manner  be  caved  and  drawn  off  without  difficulty,  but  the 
work  has  to  be  conducted  with  great  care. 

The  caving  system  as  employed  in  the  Mercur  mines  is 
suited  to  both  thick  and  thin  deposits  inclined  at  moderate 
and  low  inclinations.  It  is  especially  applicable  to  deposits 
of  uniform  thickness  where  both  ore  and  roof  or  hanging- 
wall  are  sufficiently  weak  to  break  and  cave  readily.  It  is 
equally  applicable  to  both  high-  and  low-grade  deposits. 

The  advantages  of  the  system  are: 

1.  It  has  a  wide  range  of  application  as  to  thickness  of 
deposit. 

2.  A  large  percentage  of  extraction  is  possible. 

3.  A  small  amount  of  timber  and  powder  is  used. 

4.  Safety  of  men. 

The  disadvantages  of  the  system  are: 

1.  It  is  limited  to  deposits  of  moderate  inclinations. 

2.  It  is  difficult  to  keep  different  grades  of  ore  separate. 

3.  There  is  always  danger  of  loss  of  ore  from  caving 
ground. 

4.  It  cannot  be  employed  to  advantage  where  the  top 
formations  are  hard  and  firm  and  do  not  cave  readily. 

NOTE.  —  See  Bibliography  of  Methods  of  Mining,  page  202. 


-CHAPTER  VI 

METHODS    OF    MINING    IN    WIDE    VEINS    AND 

MASSES 

INTRODUCTION 

THE  methods  of  mining  employed  in  large  deposits,  as 
wide  veins  and  masses,  often  vary  but  little  from  those  used 
in  similar  but  smaller-sized  deposits.  Mining  with  square- 
sets  as  well  as  the  filling  and  caving  methods  are  commonly 
employed  in  both  large  and  medium  sized  deposits  and  usu- 
ally with  equal  facility,  with  the  possible  exception  of  the 
first  named,  or  square-setting,  which  has  its  limitations  and 
probably  has  its  widest  range  of  usefulness  in  the  smaller 
and  medium  sized  deposits.  Square-set  mining  is  now  being 
rapidly  replaced  by  the  filling  and  caving  methods,  and  its 
use,  largely  for  economic  reasons,  will  be  relegated  to  the 
working  of  certain  deposits  of  special  shape  and  occurrence 
and  advantageously  located  with  respect  to  an  available 
supply  of  suitable  timber  or  transportation  facilities. 

The  methods  of  mining  described  and  discussed  in  this 
chapter  may  be  grouped  into  a  number  of  classes,  which 
are  arranged  in  the  following  order:  shrinkage  stoping 
methods;  square-set  methods  of  mining;  filling  methods; 
and  caving  methods. 

The  width  of  veins  considered  in  this  connection  ranges 
from  35  to  40  ft.  as  a  minimum  to  several  hundred  feet, 

while  massive  deposits  of  all  sizes  are  included. 

138 


MINING  IN  WIDE  VEINS  AND   MASSES 


139 


C/3 


140  ORE  MINING  METHODS 

SHRINKAGE  STOPING  METHODS  OF  MINING 

Shrinkage  Sloping  at  the  Gold  Prince  Mine 

The  method  employed  in  the  Gold  Prince  Mine1  located 

at  Animas  Forks,  Colorado,  illustrates  the  application  of 

1.  Gold  Prince  Mine,    overhand  stoping  to  a  very  wide  lode  of 

Animas     Forks,  . 

Colo.  low-grade  ore.     The  ore  is  free  gold  and 


3  Vein*  and  SUVer  silver  in  a  SanSue  of  Quartz  and  associated 
4.  Width  30  to  130  ft.  with  various  sulphides,  the  value  ranging 

between  $8  and  $12  per  ton.  The  lode  varies  in  width 
from  30  to  130  ft.,  averaging  probably  50  to  60  ft.  The 
wallrock  is  andesite,  usually  very  tough  and  strong. 

The  lode  is  developed  by  a  tunnel  which  cuts  it,  a  main 
level  being  driven  in  the  lode  midway  between  the  walls. 
(See  Fig.  46.)  Cross-cuts  are  driven  across  the  lode  at 
intervals  of  200  to  300  ft.  along  the  line  of  the  main  level, 
which  determine  the  width  of  the  lode,  also  the  length  of 
the  stopes.  Pillars  18  ft.  in  width  are  left  between  stopes 
through  which  raises  are  driven  forming  manways  connect- 
ing the  levels.  Openings  are  made  at  frequent  intervals 
in  these  pillars  on  either  side  of  the  manways  in  order  to 
provide  entrance  to  the  stopes.  From  the  backs  of  the 
levels,  chute-raises  are  put  up  every  30  ft.  and  extend  some 
10  ft.  vertically,  beyond  which  point  four  inclined  raises  are 
driven,  two  extending  along  the  line  of  the  lode,  the  other 
two  running  transversely  with  it  until  the  walls  are  encoun- 
tered. Stoping  is  begun  from  these  raises  and  carried  on 
both  laterally  and  vertically  until  inverted  conical-shaped 

1  The  Gold  Prince  Mine  and  Mill,  Animas  Forks,  Colo.,  by  G.  P.  Scholl 
and  R.  L.  Herrick.  Mines  and  Minerals,  vol.  27,  p.  337. 


MINING  IN  WIDE  VEINS  AND   MASSES 


141 


openings  have  been  formed,  from  the  lowermost  points  of 
which  the  chute-raises  extend  to  the  levels  below,  being  pro- 
vided with  loading  chutes  through  which  the  cars  are  rilled. 
(See  Figs.  46  and  47.)  As  the  ore  is  strong  and  solid  it 
stands  well  without  support,  and  the  thick  back  of  ore  in 
the  form  of  stump-pillars  insures  against  danger  from  caving 
ground  in  the  stopes.  Owing  to  the  width  and  length  of 
stopes,  the  work  of  stoping  can  be  carried  on  very  rapidly 


FIG.  48.  —  Vertical  Longitudinal  Section  through  Lode  Showing  Method  of 
Development  and  Working  by  Shrinkage  Stoping.  (Modeled  after  Sketch  by 
H.  T.  Hulst,  G.  R.  Jackson  and  W.  A.  Siebenthal.) 

and  at  the  same  time  the  large  masses  of  ore  or  boulders 
can  be  reduced  to  such  a  size  as  to  readily  pass  through  the 
chutes.  It  is  only  necessary  to  draw  off  about  30  per  cent 
of  the  broken  ore  to  provide  room  for  the  miners  to  work  at 
the  face,  the  remainder  being  left  in  the  stopes  if  desired,  as 
a  reserve.  The  ore  is  hard  and  dry  and  does  not,  therefore, 
pack  in  the  stopes  nor  break  up  while  being  withdrawn  there- 
from. A  stope  having  been  worked  up  to  the  level  above, 
and  the  ore  drawn  off,  an  attempt  may  be  made  to  cut  out 


142  ORE   MINING  METHODS 

the  level  or  stump-pillars,  which  can  be  done  by  under- 
hand stoping  to  a  certain  point,  after  which  there  is  danger 
of  the  stope  collapsing,  although  probably  the  greater  part 
of  the  ore  can  be  secured. 

The  method  of  mining  employed  in  the  Gold  Prince  Mine 
resembles  in  many  respects  the  practice  in  the  Alaska- 
Treadwell  mines,  although  owing  to  the  smaller  size  of 
deposit  it  is  on  a  very  much  smaller  scale.  The  method  is 
applicable  to  wide  deposits  of  low-grade  ore,  which  is  both 
hard  and  strong,  standing  without  support,  and  with  strong 
wallrock. 

The  deposit  should  also  stand  nearly  vertical  in  order 
that  the  method  may  have  the  widest  range  of  applica- 
tion. 

The  advantages  of  the  method  are: 

1.  No  timber  or  other  support  is  required. 

2.  The  output  is  large. 

3.  The  cost  of  mining  is  low. 

4.  A  reserve  of  broken  ore  is  available  at  any  time. 

5.  Handling  of  ore  is  reduced  to  a  minimum. 

6.  Ventilation  is  good. 

7.  The  workings  are  easy  of  access. 

8.  Little  development  work  is  necessary. 
The  disadvantages  of  the  method  are: 

1.  Limited  to  large  highly  inclined  deposits. 

2.  There  is  no  opportunity  to  sort  or  stow  waste  rock. 

3.  Considerable  loss  of  ore  in  pillars. 

The  application  of  shrinkage  stoping  to  a  narrower  lode  is 
shown  in  Fig.  48. 


MINING  IN  WIDE  VEINS  AND   MASSES 


144  ORE  MINING  METHODS 

Shrinkage  Sloping  at  the  Alaska-Treadwell  Mine 

The  mining  of  the  immense  deposits  of  low-grade  gold  ores 
of  the  Alaska-Treadwell  mines,  Alaska,  has  been  from 

1.  Alaska-Treadwell     the  begmning  of  their  exploitation  the  sub- 

isiand   Alaska8    Ject  °^  muc^  study  and  experimentation 

2.  Gold  Ore.  until  a  method  has  been  developed  which 

3.  Massive      deposit 

standing    verti-    seems  to  be  eminently  suited  to  the  exist- 

cally  or  nearly  so.  .  . 

4.  Thickness  several    mg  conditions. 

iet'  The  ore  occurs  in  diorite,  is  hard  and 
firm,  and  stands  well  both  in  pillars  and  stope-backs.  The 
orebodies  are  lenticular  in  shape  and  dip  from  50  to  65°, 
the  foot-wall  being  schist  and  moderately  soft,  while  the 
hanging-wall  is  greenstone  or  gabbro,  and  is  hard. 

The  method  of  developing  the  orebodies  consists  in  sink- 
ing a  shaft  in  the  foot-wall  from  which  levels  are  driven  to 
and  through  the  deposit.  At  the  intersection  of  the  levels 
with  the  foot-wall,  drifts  7  by  10  ft.  in  section  are  run  par- 
tially in  the  foot-wall  and  partially  in  the  deposit.  The 
positions  of  the  pillars  having  been  decided  upon,  those  of 
the  various  levels  being  located  vertically  one  above  the 
other,  main  raises  6  by  7  ft.  in  section  are  put  up  at  in- 
tervals of  about  200  ft.,  which  places  a  raise  in  alternate 
pillars.  These  raises  make  connection  with  the  various 
levels,  which  are  now  driven  200  ft.  apart.  The  distance 
between  levels  has  been  increased  from  no  ft.,  the  original 
distance,  to  the  height  of  200  ft.  now  employed.  Midway 
between  the  proposed  centers  of  pillars  cross-cuts  are  driven 
across  the  deposit  paralleling  the  pillars.  At  intervals  of 


MINING  IN  WIDE  VEINS  AND  MASSES  145 

60  ft.  along  the  cross-cuts,  drifts  are  run  normal  to  them 
and  parallel  with  the  longer  dimension  of  the  orebody. 
Other  raises  are  put  up  in  the  pillars  along  the  line  of  the 
level  next  to  the  hanging-wall.  The  object  of  these  raises 
is  to  ventilate  the  various  levels.  Other  raises  are  put  up 
at  25-ft.  intervals  along  both  drifts  and  cross-cuts  and  are 
termed  'chute-raises.'  At  a  height  of  18  to  20  ft.  and 
thereafter  at  intervals  of  30  ft.  'blind  drifts'  or  'sub-drifts' 


FIG.  49.  —  Vertical  Longitudal  Section  through  Lode  and  across  Stopes  Showing 
Development  Passages  and  Their  Relation  to  the  Stopes. 

are  driven  on  either  side  of  the  main  raises  and  extend  at 
right  angles  to  the  pillars.     (See  Figs.  49,  50,  and  51.) 

The  first  sub-drift  is  driven  as  a  drift-stope  across  the 
body  of  ore  lying  between  pillars,  and  as  it  is  extended 
breaks  into  the  tops  of  the  chute-raises.  The  drift-stope 
is  8  ft.  in  height,  and  when  widened  out  on  either  side  of 
the  line  of  chute-raises  it  forms  the  beginning  of  the  stope 
or  the  cutting-out  floor.  The  tops  of  the  chute-raises  are 
enlarged  into  funnel-shaped  openings  in  order  to  more 


146 


ORE   MINING   METHODS 


MINING  IN  WIDE  VEINS  AND  MASSES  147 

readily  collect  the  ore  broken  down  from  above.  The 
chute-raises  should  be  kept  full  to  protect  them  from  fall- 
ing ore. 

After  the  drift-stope  has  been  extended  from  one  pillar 
to  another  and  the  'stope  floor'  established  the  work  of 
opening  the  whole  stope  is  begun.  Drills  are  set  up  in  the 
center  of  the  stope  floor  and  a  drift-stope  is  run  longi- 
tudinally the  full  length  of  the  stope.  This  drift  stope 
is  then  enlarged  laterally  by  breast  work  until  the  pillars 
have  been  reached.  Considerable  care  is  taken  in  forming 
the  back  of  the  stope  into  an  arch  with  sufficient  curvature 
to  stand  readily.  As  previously  pointed  out,  the  character 
of  the  ore  is  such  that  it  stands  well  in  low  arches  of  wide 
span,  thus  permitting  wide  stopes  to  be  maintained.  The 
larger  fragments  of  ore  resulting  from  blasting  in  the  stopes 
must  be  reduced  by  sledge-hammers  and  small  charges  of 
powder  to  a  size  to  pass  the  chutes.  The  latter  operation 
is  known  as  'bulldozing.'  It  has  been  found  that  the 
broken  ore  requires  one-third  more  space  than  the  solid  ore, 
consequently  one-third  must  be  removed  to  provide  room 
for  the  miners  at  the  working  face.  (See  Fig.  51.) 

As  the  work  of  cutting  out  the  back  of  the  stope  continues 
the  various  sub-drifts  are  broken  into,  thus  maintaining 
access  to  the  stopes  and  providing  a  passage  for  air  currents. 
Ultimately  the  stope  breaks  into  the  level  above,  but  instead 
of  carrying  it  up  the  full  width  it  is  arched,  only  the  crown 
of  the  arch  being  broken  through.  A  ledge  is  then  left 
in  the  stope  floor  above,  which  is  supported  by  the  flaring 
tops  of  the  pillars  below.  These  ledges  are  termed  'sheet- 


148 


ORE  MINING  METHODS 


rt 

c 

T; 

p 

q 

7 
in 

o 

u 


MINING  IN  WIDE  VEINS  AND   MASSES  149 

pillars'  and  are  in  reality  pentices,  as  their  primary  object 
is  to  serve  as  a  protection  to  the  men  employed  in  the  stopes 
below. 

The  pillars  are  approximately  100  ft.  center  to  center, 
the  length  varying  with  width  of  orebody  and  may  be  300 
ft.  The  width  of  the  pillars  varies  from  1 8  to  25  ft.  and 
they  are  often  considerably  wider  especially  with  the  height 
of  stopes  now  employed.  The  height  of  the  stope  is  about 
185  ft.,  or  twice  the  width,  the  increased  height  being 
considered  more  economical,  as  fewer  levels  have  to  be 
formed. 

The  method  of  mining  employed  in  the  Alaska-Treadwell 
mines  is  applicable  to  very  large  deposits  of  low-grade,  hard 
and  firm  ore,  also  to  deposits  standing  at  high  inclinations. 

The  advantages  of  the  method  are:1 

1.  Levels  can  be  placed  far  apart. 

2.  Practically  no  timber  is  used. 

3.  Large  output  for  number  of  men  employed. 

4.  The  cost  of  extraction  of  ore  is  small. 

5.  Handling  ore  is  reduced  to  a  minimum. 

6.  Little  danger  from  accidents. 

The  disadvantages  of  the  method  are : 1 

1.  Is  applicable  only  to  large  deposits  of  high  dips. 

2.  The  stopes  must  be  carried  up  vertically. 

3.  The  amount  of  development  work  required  for  each 
level  is  large. 

4.  System  of  ventilation  is  rather  complicated. 

1  For  disadvantages  and  advantages  of  shrinkage  stoping  see:  "Shrink- 
age" Stoping,  by  F.  Percy  Rolfe.  Mines  and  Minerals,  vol.  30,  p.  210. 


ORE  MINING  METHODS 


5.  Loss  of  ore  in  pillars  rather  large,  especially  if  a  regular 
system  is  followed  in  laying  out  workings. 

For  reference  to  practice  in  Shrinkage  Stoping  see  Bib- 
liography at  end  of  chapter  on  Methods  of  Stoping. 

SQUARE-SET  METHODS  or  MINING 
Use  of  Square-Sets  at  Rosslandj  British  Columbia 
Timbering  by  square-sets,  in  which  the  members  of  the 
sets  are  unsawed  round  timbers,  is  common  practice  in 


FIG.  52.  —  Square-Sets  Composed  of  Round  Timbers. 


MINING  IN  WIDE  VEINS  AND  MASSES 


many  parts  of  the  country.       In  Fig.  52   is  shown  the 

system  of  square-setting  with  round  timbers  as  employed 

in  the  mines  of   Rossland,   British   Co-  ^  Mines  at  Rossiand, 

lumbia.    The   ore  deposits    often 

widths  ranging  up  to  100  ft.  and  dip  at 

an  angle  of  about  70°.     Both  ore  and  wall  ^  Maximum     width 

rock  are  very  hard,  the  former  being  badly 

fractured  and  fissured,  and  is  cemented  together  with  aurif- 


have         B* > 

2.  Gold    and    Copper 
Ore. 


C. —  Adaptation  of  Square-Set  Mining  to  a  Highly  Inclined  Vein,  Showing 
Ore  Bin  and  Chute  for  Loading  Cars  in  Level. 

erous  sulphides.     The  conditions  existing  in  these  deposits 
are  decidedly  favorable  for  the  employment  of  square-sets. 


152  ORE  MINING   METHODS 

Stoping  is  done  by  the  overhand  system,  the  work  being 
started  from  a  raise  or  winze  and  proceeds  in  both  direc- 
tions. The  work  is  carried  on  in  floors,  each  floor  being 
somewhat  over  a  set  high  and  terminates  in  a  back-stope, 
i.e.,  if  there  are  four  back-stopes  there  are  five  floors  includ- 
ing the  drift-stope.  The  square-sets  in  the  stopes  assume  a 
stepped  formation,  dropping  down  set  by  set  in  both  direc- 
tions from  the  raise.  The  timbers  composing  the  sets 
range  in  diameter  from  12  to  20  in.,  averaging  about  18  in., 
and  are  partially  seasoned  before  being  used  in  the  mines. 

Square-set  Mining  in  the  Queen  Mine 

Square-sets  have  been  extensively  employed  in  mining 
the  iron  ores  of  the  Lake  Superior  region,  but  have  been 

1.  Queen  Mine,          largely  superseded  in  the  massive  deposits 

Negaunee,  Mich. 

2.  iron  Ore.  by  the  caving  methods,  such  as  the  top 

3.  Massive  Deposit.     ^      sub.drift  and  modifications  of  these 

4.  Large    lens-shaped 

body-  with  the  milling  method. 

A  special  method  involving  both  the  use  of  square-sets 
and  caving  has  been  employed  in  the  various  districts  and 
is  at  present  in  successful  operation  at  the  Queen  Mine, 
Negaunee,  Michigan.  The  orebody  here  is  large  and  lens- 
shaped,  being  quite  regular.  It  has  a  dip  of  38°  to  the 
north  and  pitches  45°  to  the  west.  Owing  to  its  size  and 
regularity  it  is  especially  suited  to  systematic  and  large- 
scale  operations.  (See  Fig.  53.) 

The  deposit  is  opened  by  vertical  shafts,  and  on  the  levels 
are  well-planned  systems  of  haulage  ways  through  which 
the  empty  and  loaded  trains  of  cars  can  travel  without  in- 


MINING  IN  WIDE  VEINS  AND   MASSES  153 


VERTICAL  SECTION 


PLAN 


Fig.  53.  —  Square-set  Mining  in  Massive  Deposit. 


154  ORE  MINING  METHODS 

terference.  In  the  deposit  a  number  of  stope-faces  are 
carried  three  sets  wide,  usually  parallel  with  the  major  axis 
of  the  orebody,  and  at  intervals  of  40  ft.  (five  sets)  apart 
other  similar  stopes  are  then  run,  cross-cutting  the  former 
and  at  equal  intervals.  The  deposit  is  then  broken  up  into 
rooms  (stopes)  and  pillars;  the  former  25  ft.  wide  and  by 
continued  stoping  carried  about  50  ft.  high,  the  latter 
40  ft.  square  and  of  equal  height  with  the  stopes.  The 
stopes  are  carefully  supported  by  square-sets,  those  of  the 
upper  level  extending  to  caved  ground,  if  mining  has  pre- 
viously been  carried  on  above,  if  not  to  barren  ground. 

The  next  operation  is  the  drawing  or  robbing  of  the  pillars, 
following  which  caving  begins.  A  pillar  is  removed  by 
driving  two  drifts  through  the  base,  i.e.,  on  the  level  of  the 
stope-floor,  cross-cutting  it  into  four  equal  parts.  At  the 
point  of  intersection  of  the  drifts,  or  the  center  of  the  pillar, 
an  8  by  8-ft.  raise  is  put  up  through  the  pillar,  both  drifts 
and  raise  being  timbered  with  sets.  The  backs  of  the  drifts 
are  next  stoped  out  to  the  height  of  the  centrally  located 
raise,  thus  completely  subdividing  the  pillar  into  four  equal 
parts.  Stoping  is  then  begun  at  the  top  of  the  raise,  and  the 
upper  portions  of  the  new  pillars  formed  are  removed  to  the 
depth  of  one  set.  A  cap  of  double  length  is  placed  next  to 
the  roof  and  lagging  carefully  put  in  place  above  it.  The 
work  of  cutting  away  the  pillar  is  then  resumed,  and  other 
double-length  caps  are  placed  as  rapidly  as  possible.  On 
placing  the  second  cap  it  is  usual  to  reenforce  the  first  or 
roof  cap  by  two  timbers  set  in  A-form.  The  ore  broken  from 
the  pillars  falls  upon  lagging  placed  at  the  lower  side  sets, 


MINING  IN  WIDE  VEINS  AND  MASSES  155 

from  which  it  is  run  or  shoveled  into  cars.  That  part  of 
the  ore  obtained  from  pillar-drawing  is  mined  with  the  least 
trouble  and  expense. 

Pillars  may  also  be  removed  by  ( side-slicing/  i.e.,  by 
cutting  off  slices  from  the  sides  of  the  pillars  one  set  wide 
first  on  one  side  then  on  the  other,  or  if  that  proves  to  be 
too  risky,  the  stopes  may  be  filled  with  waste  and  the  pillars 
removed  by  top-slicing. 

The  ore  having  been  all  mined  out,  the  tracks  are  removed 
and  the  timbers  are  broken  down  by  blasting  every  second 
leg  of  the  sets,  which  starts  the  cave.  When  all  movement 
has  ceased,  the  next  level  may  be  worked  out  in  a  similar 
manner,  but  so  far  the  method  has  been  confined  to  work- 
ing out  the  upper  portion  of  deposits,  subsequent  work 
being  done  by  strictly  caving  methods. 

This  combination  method  of  square-setting  and  caving 
is  applicable  to  massive  deposits  of  hard  ore  which  stand 
well  and  to  deposits  that  occur  close  to  the  surface  and  of 
large  lateral  extent. 

The  advantages  of  the  method  are: 

1.  A  large  output  is  possible. 

2.  The  cost  of  mining  is  low. 

3.  There  is  little  danger  from  falls. 

4.  Opportunity  is  given  for  the  sorting  of  ore  if  desirable. 
The  disadvantages  of  the  method  are: 

1.  It  is  of  limited  application,  being  seldom  used  in  more 
than  one  floor. 

2.  A  large  amount  of  timber  is  required. 

3.  Loss  of  timber  is  great. 


156  ORE  MINING  METHODS 

FILLING  METHODS 
Methods  Employed  in  the  Broken  Hill  Mines 

The  economic  working  of  the  large  orebodies  of  the  lode 
of  Broken  Hill,  New  South  Wales,  Australia,1  has  necessi- 
tated radical  changes  in  methods  of  mining  until  at  present 
fully  three  different  methods  are  in  use  in  various  parts 

1.  Broken  Hill  Mines,  of  the  lode.     The  ore  is  lead-silver,  al- 

N  S  W 

2.  Lead    and    Silver  though  other  minerals  of  economic  value 
3   Ve^T  are  °ktained.     The  lode  ranges  in  width 
4.  Width 35  to  370  ft,    from   25  to  370  ft.,  averaging  probably 
70  or  80  ft.,  and  stands  nearly  vertical.     The  ore  varies 
from  very  hard  and  tough  to  very  friable,  the  wall  rock  also 
varying  somewhat  in  hardness  and  strength.     These  con- 
ditions are  responsible  for  changes  in  methods,  as  well  as 
for  the  employment  of  various  methods  in  the  different  mines 
of  the  district.     The  tendency  has  been  to  employ  methods 
in  which  timber  is  being  used  less  and  less  and  is  becoming 
of  less  importance  as  a  factor  in  the  extraction  of  ore. 

There  are  three  methods  in  use  in  these  mines  which  may 
be  employed  in  illustrating  the  gradual  change  in  working, 
showing  the  evolution  from  one  to  another  and  therefore 
having  points  of  resemblance.  These  methods  are,  in  the 
order  of  their  development,  square-setting,  the  c  open-stope, ' 
and  the  'pillar-and-stope.' 

The  application  of  square-set  timbering  as  a  means  of 
support  and  a  convenience  in  mining  and  handling  ore  in 

1  Stoping  Systems  at  Broken  Hill,  Australia,  by  A.  J.  Moore.  Mines  and 
Minerals,  vol.  27,  p.  433. 


MINING  IN  WIDE  VEINS  AND   MASSES 


the  stopes  is  well  illustrated  by  the  practice  in  this  district. 
This  system  is  employed  in  ground  that  is  not  sufficiently 
strong  to  stand  by  itself,  as  in  the  friable  sulphides.  The 
all-square-set  system  is  usually  employed  in  the  narrower 
portions  of  the  lode,  although  it  has  been  used  in  the  large 
orebodies.  The  sets  are  usually  7  by  5  by  6  ft.,  i.e.,  posts 
7  ft.,  girts  5  ft.,  and  caps  6  ft.  long,  although  in  the  Central 


158  ORE   MINING  METHODS 

and  Proprietary  mines  the  sets  are  8  by  6  by  6  ft.  When  the 
ore  is  hard  and  solid  it  may  stand  with  only  an  occasional 
supporting  prop  between  it  and  the  square-sets,  but  when 
friable  the  sets  may  have  to  be  kept  close  to  the  face.  The 
disadvantage  of  carrying  the  timbering  close  to  the  face 
is  that  blasts  are  liable  to  injure  or  knock  down  the  sets, 
which  is  expensive  from  the  standpoint  of  loss  of  timber  and 
delay,  and  may  also  result  in  falls  of  rock.  (See  Figs. 
54  and  55.) 

The  method  of  placing  lagging  for  the  miners  to  stand 
upon  while  working  at  the  face  is  shown,  also  the  arrange- 
ment of  chutes  and  pockets  for  handling  and  holding  ore 
preparatory  to  loading  it  into  cars. 

The  open-stope  method  of  mining  as  employed  in  the 
Broken  Hill  mines  is  in  successful  operation  in  portions  of 
the  lode  that  average  70  to  80  ft.  in  width  and  occasionally 
200  ft.  Where  used  the  walls  are  firm  and  the  ore  is  solid, 
standing  fairly  well  by  itself.  Owing  to  the  width  of  the 
lode,  a  portion,  usually  somewhat  less  than  one-half,  is 
left  as  a  pillar,  although  it  is  planned  to  ultimately  mine  all 
the  ore.  (See  Fig.  56.) 

The  lode  is  developed  by  vertical  shafts  sunk  in  the  foot- 
wall  from  which  levels  are  driven  some  20  to  30  ft.  from  and 
paralleling  the  lode.  From  the  foot-wall  levels,  cross-cuts 
are  driven  at  intervals  of  80  to  100  ft.  to  and  through  the 
lode  until  the  hanging-wall  is  reached,  when  they  are 
opened  up  on  either  side.  Connecting  the  cross-cuts  and 
through  the  center  of  the  lode  is  a  passage,  which  serves  as 
the  main  haulage  way.  Combined  ore  chutes  and  man- 


MINING  IN  WIDE  VEINS  AND   MASSES 


159 


ways  are  placed  every  30  ft.  along  the  haulage  way,  being 
timbered  passages  built  up  as  the  stope  increases  in  height. 


The  cross-cuts  are  timbered  with  square-sets  as  formed,  and 
are  extended  laterally  until  they  run  together,  if  that  is 
found  desirable,  thus  forming  a  long  continuous  stope. 
The  cross-cuts  and  afterward  the  stopes  are  carried  n  to  12 


i6o 


ORE  MINING  METHODS 


a. 
o 

c/p 
g 


f 

O 


MINING  IN  WIDE  VEINS  AND   MASSES  161 

ft.  high,  which  is  done  in  two  operations :  the  lower  5  or  6  ft. 
by  drifting  and  breast  stoping,  the  upper  6  ft.  by  mount- 
ing the  drills  on  a  crib-work  of  timbers.  Beginning  with 
the  foot- wall  side  of  the  lode  square-sets  are  placed,  but 
kept  far  enough  back  from  the  face  to  prevent  injury  by 
blasting.  As  an  additional  support  cribs  are  built  in  ad- 
vance of  the  sets,  thus  insuring  the  support  of  the  back 
under  ordinary  conditions.  A  method  of  extending  certain 
members  of  the  crib  that  come  next  to  the  back  as  cantile- 
vers to  support  bad  ground,  which  is  held  in  place  by  wedges, 
is  an  important  factor  in  the  system  of  control  of  back.  On 
completing  the  level  or  sill-floor  and  having  filled  the  stope  to 

within  a  few  feet  of  the  back,  the  work  of  removing  another 

i 
horizontal  slice  is  begun,  the  cutting-out  being  carried  on  as 

before,  except  that  no  sets  are  used  above  the  sill-floor,  cribs 
being  the  only  form  of  timber  support  employed.  The 
waste-filling  is  run  into  the  stopes  through  winzes  put  down 
from  the  level  above  and  spaced  100  ft.  apart  along  the 
stopes,  its  distribution  being  done  in  small  cars  operating 
on  temporary  track  laid  on  the  waste.  (See  Fig.  57.) 

Owing  to  the  ore  chutes  having  become  badly  worn  it  is 
usually  found  necessary  to  run  ore  through  the  manways 
after  a  height  of  50  ft.  has  been  reached  in  the  stope.  When 
the  stopes  have  reached  a  height  of  60  ft.,  it  is  usually  con- 
sidered advisable  to  change  the  method  of  procedure  and 
remove  the  remaining  40  ft.  by  overhand  stoping  and 
filling,  similar  to  the  filling  method  employed  in  the  mines 
at  Zaruma,  Ecuador.  Stoping  is  begun  at  the  foot  of  the 
winzes  and  carried  outward,  back-s topes  being  formed  as 


162  ORE  MINING  METHODS 

those  previously  driven  advance,  which  soon  forms  the  back 
into  faces  sloping  away  from  the  winzes.  Filling  is  run  in 
from  above,  providing  a  footing  for  the  miners  and  a  mount- 
ing for  the  drills.  The  back  may  also  be  supported,  if  found 
desirable,  by  props  or  cribs  built  on  the  sloping  sides  of  the 
fill.  Care  must  be  taken  as  the  levels  above  are  approached 
or  the  timbering  in  them  may  collapse.  To  prevent  this 


FIG.  57.  —  Cantilever-Crib  in  Wide  Slope,  Australian  Mines. 

the  back  is  removed  in  small  sections  and  cribs  placed 
beneath  the  level  timbers,  or  square-sets  may  be  employed. 
The  pillar-and-stope  method  of  mining  as  employed  in 
the  Central  Mine  is  applicable  to  great  width  of  lode  and  is 
now  operating  in  a  two  percent  orebody.  The  orebody  is 
developed  by  cross-cuts  run  from  levels  driven  in  the 
foot-wall,  which  are  connected  by  a  drift  or  level  running 
through  the  center  of  the  deposit.  S topes  are  opened  up 
from  the  levels  in  the  lode,  which  are  run  across  the  lode 


MINING  IN  WIDE   VEINS  AND   MASSES 


163 


from  wall  to  wall  50  ft.  wide  (8  sets)  and  at  intervals  of  50 
ft.,  thus  dividing  the  lode  into  stopes  and  pillars  alternately 
and  of  equal  width.  The  stope  sections  are  completely 


FIG.  58.  —  Plan  of  Pillar-and-Stope  Method  in  Broken  Hill  Mines. 

worked  out  on  the  sill-floor  and  carefully  timbered  with 
square-sets.  Winzes  are  then  put  in,  connecting  the  stopes 
with  the  level  above,  but  are  maintained  one-half  in  the 
pillar  and  one-half  in  the  stopes.  (See  Fig.  58.)  The 
outer  rows  of  sets  in  the  stopes  and  a  line  of  cross-cuts 


164  ORE  MINING  METHODS 

connecting  them  at  the  ends  of  the  stopes  are  kept  open 
by  lagging  on  the  sides  and  tops  of  the  sets.  All  other 
sets  with  the  exception  of  the  chute  sets  are  then  filled  with 
waste  and  the  work  of  stoping  out  the  back  is  begun.  This 
is  accomplished  by  the  open-stope  and  crib  method  pre- 
viously described,  the  ore  being  disposed  of  through  the 
chutes,  which  are  carried  up  to  the  full  height  of  the  stope. 
Waste  is  introduced  through  the  winzes  and  distributed 
throughout  the  stope,  filling  all  parts  except  the  two  side  rows 
of  sets,  which  are  carried  up  the  full  height  of  the  stope  and 
kept  open  in  order  that  the  waste  may  be  kept  clear  of  the  pil- 
lars and  to  permit  work  to  be  done  on  the  pillars  if  desired. 
The  stopes  are  worked  out  to  a  height  of  60  or  70  ft.,  after  which 
the  arch  pillars  are  worked  out  by  square-sets  and  filling. 

Owing  to  the  weight  of  the  ground,  which  will  have  begun 

t 

to  settle  and  move  by  the  time  the  stopes  are  worked  out, 
all  of  the  pillars  on  one  level  are  robbed  at  one  and  the  same 
time,  which  is  accomplished  by  beginning  on  the  hanging- 
wall  side  of  the  lode  and  drifting  across  from  stope  to  stope, 
the  drifts  being  timbered  with  sets  and  filled  with  waste. 
From  the  face  thus  formed  the  work  of  stoping  then  proceeds 
both  horizontally  and  vertically  until  all  the  pillars  on  a 
level  have  been  removed,  the  space  being  filled  with  square- 
sets  and  waste. 

While  the  idea  is  to  remove  ultimately  both  arch  and 
stope  pillars,  yet  such  large  quantities  of  ore  are  available 
that  so  far  little  has  been  done  except  in  the  stopes  proper. 

The  open-stope  and  pillar-and-stope  methods  of  mining 
at  Broken  Hill  are  applicable  to  very  large  lodes  of  solid, 


MINING  IN  WIDE  VEINS  AND  MASSES  165 

low-grade  ore  and  with  fairly  strong  wall  rock.  High 
inclination  of  deposit  is  also  an  important  consideration  in 
working  by  these  methods. 

The  advantages  of  the  methods  are: 

1.  Large  outputs. 

2.  Low  cost  of  mining. 

3.  Comparatively  little  timber  required. 

4.  Labor  of  handling  waste  and  ore  slight. 

5.  Opportunity  afforded  for  sorting  ore  and  stowing  waste. 

6.  Development  work  simple  and  not  extensive. 

7.  Ventilation  is  good. 

8.  Little  danger  of  accidents  from  falls. 

9.  The  complete  extraction  of  the  ore  is  aimed  at,  but 
not  attempted  at  present. 

The  disadvantages  of  the  method  are : 

1.  Applicable  only  to  large  deposits  of  low-grade  ore 
standing  at  high  dips. 

2.  Stopes  must  be  carried  vertically. 

3.  Stopes  are  of  limited  height,  usually  not  over  100  ft. 

4.  Loss  of  ore  in  pillars  large  even  if  ultimately  worked. 

METHODS  EMPLOYED  IN  THE  HOMESTAKE  MINE 
There  are  few  mines  in  the  United  States  which  have  experi- 
enced so  many  changes  in  methods  of  work-  i.  Homestake  Mine, 

.  r     ,  Lead,  South 

mg  as  have  the  Homestake  mines  of  the          Dakota. 
Black  HiUs,  South  Dakota.    The  reason  for  *•  ye°^°re' 
this  is  that  the  ores  are  low-grade,  ranging  4.  Width  30  to  soo  ft. 
from  $2  to  $12  per  ton,  and  to  operate  them  profitably  a 
large  tonnage  and  low  cost  of  mining  is  necessary. 


i66  ORE  MINING  METHODS 

The  orebodies  are  broad  zones  of  impregnations  in  schists; 
they  are  quite  irregular,  varying  from  30  to  500  ft.  in  width, 
and  usually  stand  vertically  or  nearly  so. 

Owing  to  the  great  width  of  the  deposits  the  stopes  are 
run  transversely,  extending  from  foot-wall  to  hanging-wall, 
pillars  being  left  between  the  respective  stopes.  Formerly 
it  was  customary  to  employ  square-sets  to  support  the  walls, 
which  combined  with  rilling  permitted  the  stopes  to  be 
worked  to  a  height  of  85  to  100  ft.,  the  former  being  more 
usual.  It  was  found  that  square-sets  if  carried  much  above 
85  ft.  would  often  collapse  under  their  own  weight.  With 
the  exhaustion  of  the  supply  of  suitable  timber  and  the 
consequently  increased  cost,  also  owing  to  the  gradually  de- 
creasing value  of  ore,  other  and  cheaper  methods  of  working 
the  orebodies  were  found  to  be  necessary.  While  the  general 
method  of  attack  has  not  changed  materially,  radical  changes 
in  support  have  been  made,  the  main  idea  apparently  being 
to  reduce  the  amount  of  timber  employed.  Timber  is  still 
used,  but  it  is  doubtful  whether  there  are  many  other  mines 
in  the  world  in  which  so  little  timber  is  actually  used  per 
ton  of  ore  extracted.  This  is  rendered  possible,  however, 
only  through  the  exceptionally  strong  and  solid  ore  and 
wall  rocks.  In  many  places  the  ore  stands  without  support 
in  low  arched  stopes  of  60  to  80  ft.  in  width. 

Following  the  use  of  square-sets  and  filling,  a  system  of 
back-filling  was  introduced,  being  first  employed  with  con- 
siderable timbering  in  the  form  of  timbered  passages  on  the 
ground  or  stope  floor,  but  as  the  work  is  now  carried  on  it 
would  seem  that  the  amount  of  timber  used  has  been  re- 


MINING  IN  WIDE  VEINS  AND  MASSES  167 

duced  to  a  minimum.  This  has  been  rendered  possible  by 
a  rearrangement  of  the  drifts  and  cross-cuts  through  which 
the  ore  is  withdrawn  from  the  stopes. 

Descriptions  of  two  of  the  more  recent  methods  of  mining 
are  given  below  and  will  serve  to  illustrate  the  gradual 
change  that  is  being  made  in  these  mines. 

Back-Pilling  in  the  Homestake  Mine 

In  the  first  and  earlier  method  levels  are  driven  from  100 
to  150  ft.  apart,  depending  largely  upon  the  condition  of 
the  ground  and  the  depth  of  the  workings.  The  levels 
having  been  formed  and  consisting  of  foot-wall  and  hang- 
ing-wall drifts  and  one  or  more  intermediate  drifts,  the 
work  of  opening  up  the  stope  is  begun.  This  is  accomplished 
by  carrying  a  working  face  outward  and  across  the  deposit 
from  the  drift  on  the  foot- wall  side.  The  stope  is  cut  to  a 
width  of  60  to  75  ft.  and  to  a  height  of  about  10  ft.,  the 
work  being  done  by  breast  stoping.  Other  stopes  are  begun 
along  the  line  of  the  level  drifts  at  intervals  of  25  to  40  ft., 
the  unworked  portions  serving  as  pillars  between  the  rooms  or 
stopes  on  either  side.  A  stope  having  been  cleared  of  broken 
ore,  all  lines  of  haulage  that  are  to  be  maintained  within  it 
are  carefully  timbered  and  lagged.  The  passages  that  are 
considered  necessary  for  the  proper  handling  of  the  ore  are 
the  sideways  and  endways,  the  former  being  known  as  cross- 
cuts and  the  latter  as  drifts.  The  drift  in  the  foot- wall  side 
is  timbered  with  a  double  row  of  sets.  There  are  also  one 
or  more  intermediate  passages  running  transversely  with  the 
stope  and  connecting  the  cross-cuts.  (See  Figs.  59  and  60.) 


1 68 


ORE  MINING  METHODS 


MINING  IN  WIDE  VEINS  AND   MASSES  169 

Back  stoping  is  then  begun,  usually  on  the  hanging-wall 
side,  and  carried  lengthwise  of  the  stope  for  a  distance  of 
about  14  ft.  less  than  that  of  the  first  or  level  stope.  By  this 
method  of  procedure  the  cross-cuts  are  set  into  the  pillars 
and  protected  by  them  from  movements  of  ore  in  the  stopes. 
No  attempt  is  made  to  remove  the  ore  as  it  is  broken  down, 
except  to  provide  space  for  the  miners  above,  the  excess 
being  drawn  off  from  below  along  the  line  of  the  drifts 
and  cross-cuts. 

As  the  height  of  the  stopes  increases  it  is  necessary  to 
provide  passages  for  the  men  to  and  from  the  working 
face;  this  is  accomplished  by  putting  in  raises,  which  are 
in  line  with  the  cross-cuts  and  like  them  are  set  into  the 
pillars.  These  raises  are  timbered,  and  besides  serving  as 
manways  assist  in  ventilating  the  stopes.  With  levels  100  ft. 
apart  the  stopes  are  carried  to  a  height  of  70  ft.,  at  which 
point  the  roof  is  arched,  giving  an  additional  height  of 
15  ft.,  thus  making  the  stopes  85  ft.  high  and  leaving  an 
arch  pillar  15  ft.  in  thickness.  With  greater  distance  be- 
tween levels,  the  height  of  the  stopes  is  proportionally 
greater.  Finally  raises  are  put  through  the  arch  pillars  at 
the  highest  point  of  the  stope,  thus  establishing  communi- 
cation with  the  level  above.  These  raises  are  subse- 
quently employed  in  introducing  waste  into  the  stopes 
for  filling. 

The  work  of  stoping  having  been  completed,  the  ore  may 
be  withdrawn  or  left  in  the  stope  as  a  reserve  supply  that 
may  be  drawn  upon  as  occasion  demands.  It  is  drawn  out 
of  the  stope  by  breaking  away  the  lagging  on  the  side  of 


i  yo 


ORE  MINING  METHODS 


the  sets  on  the  foot-wall  side,  thus  permitting  the  ore  to 
run  into  the  drift,  where  it  is  shoveled  into  cars  and  sent  to 
the  shaft.  In  the  course  of  time  the  foot-wall  end  of  the 
stope  is  emptied  of  ore,  and  as  the  work  continues  the 


FIG.  60.  —End  View  of  Stope  in  Homestake  Mine,  Back-Filling  Method. 
(From  Model  in  Engineering  Office  of  Company.) 


shovelers  leave  the  shelter  of  the  timbered  drifts  and  work 
in  the  open  stope.  When  sufficient  room  has  been  cleared 
of  ore  the  work  of  filling  the  stope  is  begun  and  continues 
at  a  safe  distance  behind  the  shovelers.  It  is  customary, 


MINING  IN  WIDE  VEINS  AND   MASSES  171 

however,  to  cover  the  floor  of  the  stope  with  old  timber 
previous  to  placing  the  filling.  As  an  extra  precaution 
against  accidents  dams  are  often  erected  to  check  and 
hold  back  larger  pieces  of  waste.  (See  D,  Fig.  59.)  The 
filling,  as  previously  mentioned,  is  run  into  the  stopes 
through  the  waste  chutes  formed  in  the  arch  pillars,  and  is 
similar  in  many  respects  to  the  back-filling  method  em- 
ployed in  the  Butte  mines.  Drawing  ore  from  the  stopes 
is  not  confined  to  the  drifts  and  intermediate  passages,  but 
may  be  carried  on  along  the  line  of  the  cross-cuts.  The 
ore  having  been  completely  drawn  from  the  stope,  the  work 
of  filling  is  continued  until  the  curve  of  the  arch  is  reached, 
when  the  filling  is  leveled  preparatory  to  placing  square- 
sets,  which  are  employed  in  removing  the  arch  pillars. 

The  arch  pillars  are  removed  by  overhand  stoping  and 
square-setting,  the  work  being  done  in  sections  running 
transversely  with  the  stope.  As  the  floor  of  the  stope 
above  is  approached  considerable  care  must  be  taken  to 
prevent  falls,  but  if  the  mat  of  timber  has  been  properly 
placed  there  is  not  much  danger,  provided  the  roof  is  re- 
moved in  small  sections.  As  each  section  across  the  stope 
is  cut  out  to  the  stope  above  and  timbered,  it  is  filled  with 
waste,  and  work  on  another  section  is  begun.  It  is  ob- 
viously necessary  to  sacrifice  the  timber  employed  in  re- 
moving the  arch  pillars,  which  is  practically  all  that  is  lost, 
the  parts  of  the  sets  employed  in  the  drifts,  cross-cuts  and 
raises  being  used  again  and  again  until  broken,  when  they 
are  employed  in  making  the  timber  mat. 


172  ORE  MINING  METHODS 

More  Recent  Practice 

Owing  to  the  weakening  of  pillars  by  under-cutting  them 
for  the  cross-cuts  and  by  the  vertical  cuts  for  raises,  also  for 
reasons  of  economy  in  the  use  of  timber,  a  further  change  was 
considered  necessary.  The  present  method  of  mining,  which 
has  recently  been  introduced,  has  had  these  objectionable  fea- 
tures largely  eliminated,  and  with  slight  modifications  is  be- 
ing used  extensively  where  its  application  seems  advisable. 

In  this  method  the  orebody  is  divided  into  stopes  and 
pillars,  the  former  being  60  ft.  wide,  the  latter  42  ft.,  thus 
giving  the  pillars  approximately  ico-ft.  centers.  Through 
the  center  of  each  pillar  a  drift  6  ft.  wide  is  run,  from 
which  cross-cuts  are  driven,  one  about  midway  of  the  pillar 
and  the  others  spaced  at  intervals  of  30  ft.  on  either  side. 
Only  one  passage  is  maintained  in  the  stopes,  which  is 
timbered  extending  along  the  hanging-wall  side,  the  main 
drive  or  level  being  driven  in  the  foot-wall  some  distance 
from  the  deposit.  (See  Fig.  61.)  Raises  are  put  up  as 
timbered  passages  in  the  stopes  and  at  points  opposite  the 
cross-cut  openings,  but  on  one  side  of  the  pillars  only.  They 
are  placed  a  few  feet  distant  from  the  pillars,  but  stand 
wholly  within  the  stopes,  and  are  surrounded  by  broken  ore. 
Stoping  is  carried  on  in  a  manner  similar  to  that  previously 
described  for  the  earlier  method  employed.  The  levels  are 
usually  run  150  ft.  apart,  making  the  arched  stopes  some 
135  ft.  high.  The  arch  pillars  are  removed  by  overhand 
stoping  and  square-sets. 

Ore  is  drawn  from  the  stopes  by  shoveling  from  the 
cross-cuts  and  driveways  connecting  the  drifts  in  the  pil- 


MINING   IN   WIDE  VEINS  AND   MASSES 


173 


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174  ORE  MINING  METHODS 

lars.  The  stopes  in  this  method  of  mining  may  be  likened 
to  huge  ore  pockets,  the  cross-cuts  being  chutes  through 
which  the  ore  is  drawn  off.  Filling  follows  the  withdrawal 
of  the  ore,  beginning  with  the  hanging-wall  side,  its  intro- 
duction into  the  stope  being  accomplished  as  described  for 
the  earlier  method,  but  the  passages  through  which  filling 
is  brought  to  the  waste-raises  is  not  shown  in  the  sketches, 
being  omitted  for  fear  of  confusing  them  with  the  develop- 
ment openings.  It  is  the  intention  where  possible  to  re- 
move the  pillars  after  the  ore  has  been  drawn  and  the  stopes 
filled.  To  accomplish  this  to  the  best  advantage  the  sides  of 
the  pillars  are  laced  for  a  height  of  1 5  to  20  ft.,  beginning  with 
the  floor,  which  is  done  before  filling  the  stope  with  broken  ore 
and  may  be  carried  upward  as  the  stope  increases  in  height. 
The  lacing  consists  of  8  by  8  in.  timbers  placed  vertically,  to 
which  slabs  and  planks  are  spiked.  The  lacing  assists  in 
holding  back  the  waste-filling  and  prevents  mixing  with  the 
ore  as  it  is  broken  in  the  work  of  stoping  out  the  pillars. 
Where  the  stope  extends  above  the  lacing  the  waste  may  be 
held  back  temporarily  by  facing-boards  and  props.  Square- 
sets  may  be  employed  in  removing  the  pillars.  (See  Fig.  62.) 

Considerable  ore  may  be  lost  in  drawing  it  from  the 
stoped  pillars,  especially  during  the  latter  part  of  the 
operation.  This  disadvantage  may  be  largely  overcome  by 
removing  the  ore  as  broken  and  placing  filling  at  once. 

The  methods  of  mining  employed  in  the  Homestake  mines, 
as  described  above,  are  applicable  to  very  large  deposits  of 
low-grade  ore,  both  ore  and  wall  rock  being  hard  and  strong, 
permitting  wide  low-arched  stopes  to  be  worked  with  safety. 


MINING  IN  WIDE  VEINS  AND   MASSES 


175 


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176  ORE  MINING  METHODS 

V 

The  advantages  of  the  methods,  but  with  special  refer- 
ence to  the  last  described,  are: 

1.  Levels  may  be  placed  a  considerable  distance  apart. 

2.  Little  timber  is  used. 

3.  Ore  is  broken  at  small  cost. 

4.  Shovelers  are  well  protected. 

5.  Filling  is  easily  and  cheaply  placed. 

6.  Percentage  extraction  is  high. 

7.  Amount  of  development  work  is  small. 

8.  Large  outputs  are  easily  obtainable. 
The  disadvantages  of  the  methods  are: 

1 .  Applicable  only  to  wide  deposits  standing  nearly  vertical. 

2.  The  work  must  be  carried  along  vertical  lines. 

3 .  As  the  ore  breaks  in  large  masses  considerable  hand  work 
must  be  done  in  reducing  to  proper  size  to  be  loaded  into  cars. 

4.  The  method  requires  considerable  handling  of  ore. 

5.  The  loss  of  ore  in  pillars  is  large  unless  they  are  ulti- 
mately removed. 

CAVING  METHODS 

During  the  comparatively  short  time  that  iron  ore  has 

been  mined  in  the  Lake  Superior  region  many  changes  in 

i    NO  Local  Appiica-  methods    have    been    made,  which    con- 

tlon-  dition  of  affairs  has  been    brought  about 

2.  Iron  Ore. 

3.  Massive  Deposits  largely   by   experience   in   mining   under 

and  Veins.  . 

4.  Width  of  veins  40  varying  conditions,  lack  of  suitable  tim- 

ber and  a  demand  for  cheaper  ore.  There 
are,  however,  two  methods  of  mining  that  have  been  em- 
ployed for  many  years,  and  while  modified  from  time  to 


MINING  IN  WIDE  VEINS  AND  MASSES  177 

time  to  meet  certain  conditions,  they  remain  fundamentally 
the  same.  These  are  the  top-slice  and  sub-drift  methods.1 
No  local  application  will  be  made  in  the  descriptions  of 
these  methods,  other  than  to  state  that  they  are  applied 
equally  well  to  wide  veins  and  masses  of  considerable  extent. 
Veins  ranging  in  width  from  40  to  80  and  100  ft.  and  with 
dips  of  60  to  80°  may  be  readily  worked  by  both  methods. 
The  development  of  the  deposits  is  the  same,  except  as  to 
the  work  in  the  vein,  consisting  of  inclined  or  vertical 
shafts  sunk  in  the  foot-walls  of  veins  or  in  the  firm  ground 
some  distance  from  masses  of  ore,  levels  being  50  to  75  ft. 
apart. 

The  Top-Slice  Method 

In  the  top-slice  method,  after  the  cross-cuts  from  the 
shaft  have  reached  and  been  driven  into  the  deposit,  main 
levels  intersecting  them  are  run  through  the  center  of  the 
orebody,  being  connected  at  intervals  of  100  ft.  by  two 
compartment  raises.  These  raises  contain  an  ore  chute  and 
a  manway,  the  latter  being  also  used  for  handling  timber, 
and  are  put  up  to  barren  or  to  caved  ground  as  the  case 
may  be.  Beginning  at  the  top  of  the  raise  driven  from 
a  level,  a  drift  is  run  parallel  with  the  main  level  below 
and  from  both  sides  of  the  raise.  (See  Figs.  63  and  64.) 
If  the  work  is  carried  on  systematically  these  drifts  should 
meet  other  drifts  similarly  driven  from  adjacent  raises, 
or  encounter  caved  ground,  the  ore  having  been  mined  out. 
Cross-cuts  are  turned  off  at  the  ends  of  the  drifts  and  the 

1  The  Top-slice  and  Sub-drift  Methods  of  Caving  Iron  Ore,  Lake  Su- 
perior Region.  Mineral  Industry,  vol.  3,  pp.  384,  392,  1894. 


i78 


ORE  MINING  METHODS 


ore  removed  to  the  vein  walls.  These  drifts  and  cross-cuts 
must  be  carefully  timbered,  the  sets  often  being  given  double 
posts.  The  ore  is  hauled  to  the  chute  in  small  cars  and  in 
some  cases  handled  in  wheelbarrows.  The  cross-cuts  having 
been  run  to  the  walls,  a  mat  of  timber  is  placed  on  the  floor, 


MINING  IN  WIDE  VEINS  AND   MASSES 


179 


PLAN  OF 


1 
.  -"' 
TOP-SLICE  METHOD 


LONGITUDINAL  ELEVATION 
TOP-SLICE 


Fig.  64. —  Plan  and  Longitudinal  Section  of  Top-slice  Method. 


i8o  ORE  MINING  METHODS 

consisting  of  three  long  stringers  laid  next  to  the  posts  of  the 
sets  and  midway  between  them,  upon  which  in  turn  are 
placed  split  lagging  and  slabs.  This  mat  of  timber  sup- 
ports the  caved  material  when  a  drift  is  run  beneath  it. 
To  facilitate  the  work  of  placing  the  mat,  the  cross-cuts 
are  driven  in  only  one  direction  at  a  time,  thus  permitting 
the  placing  of  the  mat  in  the  finished  cross-cuts  on  one 
side  of  the  drift.  (See  Plan  of  top-slice,  Fig.  64.)  The 
mat  having  been  placed,  the  sets  are  blasted  out,  permitting 
the  roof  to  cave  close  up  to  the  ends  of  the  pillars.  Other 
cross-cuts  are  then  opened  up  at  the  ends  of  the  drifts 
adjacent  to  the  caved  ground,  the  same  process  of  cutting 
out,  timbering,  placing  mat  and  caving  the  ground  being 
repeated.  This  is  continued  until  the  pillars  are  entirely 
removed,  when  the  drift  is  of  necessity  closed  and  a  new 
drift  is  opened  up  at  the  top  of  the  raise  as  was  previously 
done,  and  work  on  a  new  slice  is  begun.  Timber  is  hoisted 
through  the  manways  to  the  slicing  drifts. 

The  top-slice  method  is  applicable  to  large  bodies  of 
cheap  ore,  which  may  be  hard  or  moderately  soft.  If  veins 
are  worked  they  should  have  a  dip  not  less  than  60°. 

The  advantages  of  the  method  are: 

1.  Development  is  simple  and  quickly  done. 

2.  Opportunity  is  afforded  for  sorting  ore,  as  keeping 
Bessemer  and  non-Bessemer  ores  separate. 

3.  Practically  the  complete  extraction  of  ore  is  possible. 

4.  Ventilation  is  good. 

5.  Little  danger  of  accidents  from  falls. 

6.  Cost  of  mining  is  low. 


MINING  IN  WIDE  VEINS  AND  MASSES  181 

The  disadvantages  of  the  method  are: 

1.  Number  of  working  places  limited,  thus  limiting  out- 
put. 

2.  Levels  are  close  together. 

3.  Considerable  timber  is  required. 

4.  Much  handling  of  ore  and  timber  is  necessary. 

5.  Confined  to  deposits  close  to  the  surface. 

Sub-Drift  Method 

The  sub-drift  method,  while  employed  in  the  same  district 
and  even  in  the  same  mines  as  the  top-slice,  differs  radically 
from  it  both  in  methods  of  development  within  the  deposit 
and  in  working.  The  development  of  a  wide  lode  which  is 
to  be  worked  by  the  sub-drift  method  is  shown  in  Fig.  65. 
A  main  level  is  run  in  the  deposit,  near  the  foot- wall,  con- 
necting the  points  where  the  cross-cuts  from  the  shaft  enter 
the  lode,  from  which  passages  are  driven  at  intervals  of 
about  50  ft.,  cross-cutting  the  lode.  A  second  main  level 
is  then  run  close  to  the  hanging-wall  and  connected  with 
the  cross-cutting  passages.  The  ore  on  the  levels  is  thus 
cut  up  by  means  of  the  drifts  and  levels  into  blocks  some 
50  ft.  wide  and  the  full  width  of  the  lode  in  length.  At 
5o-ft.  intervals  along  the  line  of  the  main  levels,  raises  are 
put  up  from  which  drifts  are  driven,  forming  the  so-called 
sub-drifts.  Beginning  at  a  lower  level  than  is  being  worked, 
a  raise  is  put  up  for  a  height  of  6  or  8  ft.  and  timbered,  after 
which  two  drift  sets  are  placed  and  lagged  over,  thus  form- 
ing the  starting  point  of  sub-drifts  which  are  driven  in  both 
directions,  ultimately  making  connection  with  other  drifts 


182 


ORE  MINING  METHODS 


driven  from  adjoining  raises.  As  soon  as  the  ' subs'  are 
well  started  the  raise  is  put  up  another  6  or  8  ft.  and  a  sec- 
ond set  of  subs  is  begun.  The  operation  of  putting  up  raises 
and  driving  subs  is  continued  until  the  raises  break  through 


FIG.  65.  —  Vertical  Transverse  Section  across  Lode  Showing  Method  of 
Development  in  Sub-Drift  Method. 

into  the  level  above  and  the  subs  have  made  connection 
with  other  subs.  It  is  then  evident  that  when  all  the  subs 
and  raises  have  been  completed  the  ore  between  two  ad- 
joining levels  is  honeycombed  by  both  horizontal  and  vertical 
passages  and  is  ready  for  the  last  stage  of  the  operation  of 


MINING  IN  WIDE  VEINS  AND  MASSES  183 

extraction  of  the  ore.  Sub-drifting  is,  then,  preliminary 
development  work  in  the  deposit  itself,  and  is  an  interme- 
diate operation  between  the  opening  01  the  deposit  by  shafts, 
cross-cuts,  levels,  etc.,  and  the  actual  work  of  breaking  down 
the  ore.  (See  Fig.  66.)  The  height  of  the  respective  subs 
is  the  distance  from  the  floor  of  one  to  that  of  another 
directly  above  it,  and  varies  from  12  to  15  ft.,  depending 
largely  upon  the  character  and  condition  of  the  ore. 

The  work  of  sub-drifting  is  followed  by  the  removal  of 
ore  from  the  pillars  standing  between  the  subs  and  the 
cross-cuts,  also  that  standing  in  the  back  above  the  level  of 
the  tops  of  the  subs,  and  is  commonly  known  as  'stripping/ 
Consider  that  the  work  of  stripping  has  reached  the  point 
shown  in  the  longitudinal  section,  Fig.  66.  By  knocking 
down  the  supporting  posts,  as  shown  at  the  left  of  the  first 
sub,  the  back  of  ore  will  fall  and  can  be  shoveled  up  and 
hauled  away  to  the  chutes.  The  settlement  of  the  broken 
rock  above  is  controlled  by  the  mat  of  timbers  which  is 
constantly  being  added  to  by  the  timbers  in  the  subs  that 
are  lost  and  broken.  The  method  of  cutting-out  the  pil- 
lars is  shown  in  the  plan,  Fig.  66,  as  at  the  left  where  the 
stubs  of  pillars  are  being  removed,  the  back  standing  on 
posts.  As  a  sub  cannot  be  worked  beneath  others  not 
yet  removed,  it  is  necessary  to  either  entirely  remove  the 
upper  sub  before  beginning  work  on  a  lower  one,  or  to 
carry  on  the  stripping  in  descending  order,  each  sub  being 
carried  some  distance  in  advance  of  the  one  below.  (See 
Fig.  67.) 

As  soon  as  the  stripping  operation  reaches  a  main  level 


1 84 


ORE   MINING  METHODS 


PLAN  OF  THIRD   SUB-DRIFT 

Fig.  66.— Longitudinal  Section  and  Plan  of  Sub-drift  Method. 


MINING  IN  WIDE  VEINS  AND  MASSES 


185 


that  level  is  abandoned  and  all  communication  with  the 
subs  below  must  be  through  the  lower  level.  The  usual 
practice  is  to  have  one  level  or  lift  (the  block  of  ore  between 


FIG.  67.  —  Vertical  Longitudinal  Section  through  Lode  Showing  Method  of 
Development  and  Working  of  Sub-Drift  Method. 

levels)  in  the  process  of  stripping;  the  next  lower  sub- 
drifting,  while  the  third  lift  below  is  being  opened  up  by 
cross-cuts.  The  ore  will  also  have  to  be  run  through  the 
chutes  from  the  upper  to  the  lower  sub.  In  order  to  facili- 


1 86  ORE  MINING  METHODS 

tate  the  handling  of  timber  it  is  brought  in  from  the  upper 
level  and  lowered  to  the  respective  subs  instead  of  being 
raised  as  in  the  top-slice  method. 

Light  but  close  timbering  is  the  rule  and  by  careful  work 
the  caving  ground  can  be  controlled  with  little  or  no  danger 
of  crushes  and  loss  of  ore. 

Sub-Drifting  in  Panels 

The  work  of  mining  by  the  sub-drift  method  as  described 
is  for  comparatively  hard  and  strong  formations,  but  when 
soft  and  unstable  formations  are  encountered,  either  the 
method  will  have  to  be  modified  to  meet  the  special  condi- 
tions or  a  change  of  method  will  be  necessary.  The  method 
of  working  by  sub-drif ting  as  employed  at  the  Susquehanna 
Mine  at  Hibbing,  Minnesota,  is  shown  in  Fig.  68. 

On  approaching  the  limits  of  the  orebodies  in  this  mine 
masses  of  clay  and  sand  are  encountered,  which  unless  care- 
fully controlled  will  break  into  and  fill  the  workings.  A 
block  of  ore  or  panel  is  shown,  the  opening  up  of  which  has 
developed  the  bad  condition  of  the  ground,  which  is  under 
control  by  the  employment  of  dams  in  the  drifts  and  cross- 
cuts and  even  at  the  face  where  stripping  is  being  done. 
Two  sets  of  dams  are  shown,  which  were  found  necessary 
in  order  to  hold  back  the  clay  and  sand.  The  dams  are  built 
of  one-inch  pine  boards  strongly  reenforced  by  backing 
strips  and  braces.  The  method  of  attacking  the  pillars  is 
shown  by  the  arrows.  The  back  varies  from  8  to  12  ft.  in 
thickness,  and  is  caved  by  blasting  out  three  sets  at  a  time, 
thus  bringing  the  cave  to  within  one  set  of  the  working  face. 


MINING  IN  WIDE  VEINS  AND  MASSES 


187 


VIOOd 


T1V/W 


i88 


ORE  MINING  METHODS 


The  timber  used  for  sets  in  this  mine  is  8  to  10  in.  in  diameter, 
the  floor  being  covered  with  rough  pine  boards  upon  which 
the  sets  stand.  These  boards  render  shoveling  easy  and 


D.  —  Vertical  Longitudinal  Section  through  Body  of  Iron  Ore  Showing  Method 
of  Development  and  Working  of  Sub- Drift  or  So-called  Sub-Level  Method. 
(Modeled  after  Sketch  by  Frank  Kennedy.) 

make  a  good  mat  in  controlling  the  movement  of  broken 
ground  and  waste  ore. 

The  sub-drift  method  of  mining  is  applicable  to  both 
hard  and  moderately  soft  ores,  preferably  the  former,  but 


MINING  IN  WIDE  VEINS  AND  MASSES  189 

not  to  mixed  ores  as  where  Bessemer  and  non-Bessemer  ores 
occur  together.     It  is  strictly  large-scale  work  and  may  be 
applied  to  massive  deposits  or  large  lodes  of  cheap  ore. 
The  advantages  of  the  method  are: 

1.  Large  outputs  are  possible  owing  to  the  large  number 
of  points  of  attack. 

2.  Cost  of  mining  is  low. 

3.  The  complete  extraction  of  ore  is  practically  possible. 
The  disadvantages  of  the  method  are: 

1.  Much  timber  is  required. 

2.  Development  work  is  extensive  and  complicated. 

3.  Little  or  no  opportunity  is  afforded  for  sorting  ore. 

4.  Considerable  handling  of  ore  and  timber  is  necessary. 

5.  Ventilation  is  poor. 

6.  Stripping  operation  is  rather  dangerous. 

7.  It  is  confined  to  deposits  lying  close  to  the  surface. 

8.  It  is  limited  to  comparatively  hard  ores. 

Shrinkage  Sloping  at  Miami  Mine 

The  employment  of  the  shrinkage  stoping  method  to  mas- 
sive deposits  is  shown  to  good  advantage  in  the  mine  of  the 
Miami  Copper  Company  at  Miami,  Arizona.1  The  stopes 
worked  in  this  mine  have  dimensions  of  50  ft.  in  width  by 
200  to  500  ft.  in  length,  with  an  average  height  of  125  ft. 

Owing  to  the  large  amount  of  ore  tied  up  in  the  pillars 
which  would  be  lost  through  caving  and  mixing  with  the 
capping  material,  a  method  of  mining  all  or  a  large  part  of 

1  For  detailed  description  of  method  see  Stoping  Methods  of  Miami 
Copper  Company.  Bull.  No.  114,  Am.  Inst.  Mining  Engrs.,  June  1916, 
p.  1031. 


IQO  ORE  MINING  METHODS 

the  pillars  has  been  devised.  The  removal  of  pillars  is 
accomplished  by  means  of  a  retreating  system,  the  pillars 
being  worked  in  levels  from  above  downward. 

The  ore  deposit  of  the  Miami  Mine  is  a  large  conical 
shaped  mass  with  its  axis  dipping  to  the  northeast  at  an 


FIG.  69.  —  Vertical  Section  across  Stopes  in  Shrinkage  Method  Employed  in  the 
Miami  Copper  Mine,  Arizona.     (Modeled  after  Sketch  by  David  B.  Scott.) 

angle  of  about  50°.  The  orebody  occurs  in  schist  in  which 
the  mineral  chalcocite  exists  in  fine  grains  and  in  seams. 
The  orebody  is  developed  by  tunnels  driven  from  shafts 
establishing  the  tramming  or  haulage  levels,  above  which 
drawing-off  levels  are  opened.  In  order  to  facilitate  han- 
dling of  ore  on  the  levels,  a  separate  level  is  run  on  either 
side  of  the  orebody,  the  two  being  connected  by  cross-cuts 
which  determine  the  center  lines  and  main  axes  of  the  stopes 
and  pillars.  The  two  sets  of  passages,  namely,  the  haulage 


MINING  IN  WIDE  VEINS  AND  MASSES  191 

ways  and  drawing-off  levels,  are  connected  by  vertical  chute 
raises,  25  ft.  long,  through  which  the  broken  ore  is  transferred 
to  the  haulage  level.  All  ore  regardless  of  its  source,  i.e.,  stope 
or  pillar,  is  passed  through  the  chute  raises,  which  must  there- 
fore be  well  protected  by  cribbing.  (See  Figs.  69  and  70.) 

Vertical  raises,  known  as  pillar  raises,  are  driven  upward, 
at  intervals  of  50  ft.  along  the  drawing-off  levels,  thr  ugh 
the  middle  of  the  portions  of  the  orebody  to  be  left  tempo- 
rarily as  pillars,  which  extend  transversely  across  the  deposit 
following  the  lines  of  the  cross-cuts.  At  a  vertical  distance  of 
25  ft.  above  the  drawing-off  levels  sublevels  are  driven  from 
the  pillar  raises  across  the  pillars  and  normal  to  the  cross- 
cuts. Other  sublevels  are  driven  in  a  similar  manner  and 
at  25  ft.  intervals  vertically,  which  give  access  to  the  faces 
of  the  stopes  as  they  are  broken  into  by  subsequent  stoping 
operations.  The  first  sublevels  determine  the  level  of  the 
floors  of  the  stopes  and  when  enlarged  laterally  by  breast 
stoping  establish  the  stope  floors.  Ready  access  to  the 
stope  faces  is  thus  maintained  and  ventilation  is  materially 
aided.  (See  Figs.  69  and  70.) 

The  stope  raises  are  begun  on  the  sides  of  the  cross-cuts  of 
the  drawing-off  level  and  at  points  where  the  chute  raises 
connect  with  the  cross-cuts,  and  are  driven  at  an  angle  of 
about  60°  to  the  stope  floors  above.  The  stope  floors  are 
50  ft.  above  the  main  haulage  levels  and  are  connected  with 
them  by  means  of  the  inclined  and  vertical  raises  through 
which  the  broken  ore  is  passed  and  its  movement  controlled. 

When  the  stope  raises  have  made  connection  with  the 
stopes,  they  are  enlarged  by  funneling  at  the  top  which 


1 92  ORE  MINING  METHODS 

constitutes  the  first  operation  in  the  work  of  stoping,  and 
when  completed  the  stope  floors  are  perforated  with  funnel- 
shaped  openings  extending  in  two  lines  along  the  stopes. 

The  first  sublevels  on  entering  the  limits  of  the  stopes  are 
widened  out  and  the  backs  of  the  levels  next  to  the  sides 
of  the  stopes  are  broken  down  by  long  holes  and  heavy 


liiSfes  M^MiiMfitt™! 


f\. ,:.;  •    •', .'  .    .-.  »  .;  ..«  »,•«.-  i»»; .  •  v; 


FIG.  70. — Vertical  Longitudinal  Section  through  Pillar,  Showing  Method  of 
Mining  Pillars.  At  the  top  is  broken  cap-rock,  next  below  broken  ore  and 
below  that  in  turn  is  the  unmined  pillar,  which  is  being  worked. 


shots;  the  result  is  that  the  middle  portions  of  the  stope- 
backs  stand  as  downward  projecting  ribs.  These  ribs  are 
next  drilled  and  shot  down,  thus  evening  up  the  backs 
of  the  stopeSo  It  is  obvious  that  the  ore  must  be  strong  or 
it  would  not  stand  without  arching,  but  the  particular  ad- 
vantage of  forming  the  ribs  of  ore  is  to  permit  the  weight 
to  assist  in  breaking  them  down.  This  method  of  breaking 


MINING  IN  WIDE  VEINS  AND  MASSES  193 

down  the  stope  backs  is  continued  from  one  sublevel  to  the 
next  above  it.  until  the  full  height  of  the  stope  is  reached, 
when  the  stope  stands  practically  full  of  broken  ore,  thus 
providing  a  large  reserve  to  be  drawn  upon  as  needed. 

The  excess  ore  is  drawn  from  the  stopes  through  the  stope 
raises,  the  larger  pieces  being  '  bull-dozed '  to  prevent  trouble 
in  the  raises. 

Stoping  is  usually  carried  upward  to  a  height  of  125  ft.,  i.e., 
until  the  capping  is  reached  or  the  level  above  is  broken  into. 

In  mining  the  pillars  the  work  of  breaking  ore  is  begun  on 
the  top  sublevel  and  continued  downward  from  sublevel  to 
sublevel  by  the  retreating  method,  i.e.,  beginning  at  one 
end  of  a  pillar  the  ore  standing  above  the  top  sublevel  is 
broken  down  by  overhand  stoping  and  after  the  working  face 
has  advanced  about  100  ft.  work  on  the  next  lower  sublevel 
is  begun.  The  development  work,  in  the  shape  of  pillar 
raises  and  sublevels,  that  was  previously  done  for  the 
opening  and  working  of  stopes  provides  the  points  of  attack 
for  pillar  drawing  and  at  the  same  time  determines  the 
thickness  of  the  respective  layers  of  floors  removed.  Fur- 
ther development  work  in  the  shape  of  pillar  raises  spaced 
at  intervals  of  25  ft.  between  the  first  raises  are  driven, 
which  with  sublevels  driven  from  them  both  increases  the 
points  of  attack  of  the  ore  in  the  pillars  and  outlets  for  the 
discharge  of  broken  ore.  (See  Fig.  70.) 

Owing  to  the  excessive  weight  thrown  upon  the  pillars 
by  the  stoping  operations  and  later  by  the  cutting  away  of 
the  tops  of  the  pillars,  it  has  been  found  necessary  to  work 
the  pillars  rapidly  and  continuously. 


194  ORE  MINING  METHODS 

The  ore  between  the  first  sublevel  and  the  capping  is 
removed  for  a  height  of  about  15  ft.,  thus  leaving  10  ft. 
beneath  the  capping  or  the  level  above,  which  is  done 
mainly  to  prevent  the  mixing  of  ore  and  cap-rock.  Further, 
to  prevent  waste  rock  from  the  caving  ground  above  from 
entering  the  pillar  raises  through  which  ore  is  being  passed, 
they  are  covered  with  bulkheads  of  timber  in  the  shape  of 
stulls  and  lagging  placed  in  the  raises  and  several  feet  below 
the  floors  of  the  sublevels. 

No  withdrawal  of  ore  from  s topes  and  pillars,  except 
that  necessary  for  providing  room  for  mining,  is  attempted 
until  at  least  70  per  cent  of  both  stope  and  pillar  work  has 
been  completed,  and  further  no  drawing  of  ore  is  permitted 
closer  than  100  ft.  from  the  s  toping  operations. 

The  method  of  mining  employed  in  the  Miami  mine  is 
adapted  to  large  bodies  of  low-grade  ore  where  sorting  of 
waste  is  not  necessary.  The  ore  must  be  strong,  however, 
and  the  enclosing  rock  must  also  be  strong  and  tough. 

The  advantages  of  the  method  are: 

1.  Large  outputs  are  possible. 

2.  Mining  cost  is  low. 

3.  A  comparatively  small  amount  of  timber  is  used. 

4.  Ore  is  handled  with  little  labor. 

5.  The  main  levels  may  be  spaced  a  considerable  distance 
apart. 

6.  There  is  little  danger  from  falls. 

7.  A  large  extraction  of  ore  is  possible. 

8.  Ventilation  is  fairly  good. 

9.  There  is  ready  access  to  and  from  the  stopes. 


MINING  IN  WIDE  VEINS  AND   MASSES  195 

The  disadvantages  of  the  method  are: 

1.  The  method  is  applicable  to  large  deposits  only. 

2.  A  large  amount  of  development  work  is  necessary. 

3.  Loss  of  ore  may  be  considerable  through  mixing  with 
waste. 

4.  Much  of  the  timber  used  is  lost. 

Sub-Drift  Method  in  the  Diamond  Mines  of  South  Africa 
The   diamond  mines  of   South   Africa1  are  particularly 

interesting  from  the  standpoint  of  economic  mining,  which 

has  been  rendered  possible  by  the  appli- 

f  .  ,  1.   Kimberly  Dia- 

cation  of  a  caving  system  operated  on  a       mond  Mines, 
large    scale.     The    deposits    of    diamond-  2   Di^o^-bearing 
bearing  material  occur  in  ducts  or  pipes       ™ck' 

«f.   iripes. 

which  stand  vertically  or  nearly  so  and  4.  Several  acres  in 

lateral  extent.    . 

penetrate  a  number  of  formations  for  a 
known  depth  of  several  thousand  feet.  (See  Figs.  71  and 
72.)  The  pipes  are  roughly  round  or  oval  in  shape,  and 
vary  in  area  at  the  surface  from  a  few  to  50  acres.  The 
walls  with  the  exception  of  the  black  shale  are  fairly  strong 
and  stand  well.  The  shale  presents  the  greatest  difficulty 
to  mining,  as  it  weathers  rapidly  and,  falling  into  the  open- 
cuts,  follows  the  diamond-bearing  ground  downward  as  it  is 
mined  out  from  below.  For  plan  see  Fig.  73. 

In  order  that  the  method  of  mining  now  employed  in 
these  mines  may  be  readily  understood,  as  well  as  the 
reason  for  its  employment  we  shall  describe  the  method  of 
working  by  galleries  as  previously  employed. 

1  The  Diamond  Mines  of  South  Africa,  by  Gardner  F.  Williams.  Chap- 
ter XI. 


196 


ORE  MINING  METHODS 


The  pipes  were  intersected  by  cross-cuts  extending  from 
shafts  sunk  in  the  rim-rock,  which  cross-cuts  were  spaced 
1 50  to  200  ft.  apart  vertically,  thus  establishing  levels  in  the 


deposits.  Intermediate  or  sublevels  were  run  from  winzes 
connecting  the  main  levels  and  spaced  30  ft.  apart  verti- 
cally. On  each  level  two  or  more  passages  were  driven 
parallel  with  the  axis  of  the  deposit  and  spaced  120  ft.  apart. 


MINING  IN  WIDE  VEINS  AND  MASSES 


197 


198 


ORE  MINING  METHODS 


MINING  IN  WIDE  VEINS  AND  MASSES  199 

From  these  passages  and  connecting  cross-cuts  galleries  18 
ft.  wide  and  high  were  driven  at  intervals  of  36  ft.,  and  were 
worked  to  within  12  ft.  of  the  sublevels  above,  and  the  upper- 
most to  within  12  ft.  of  the  loose  ground.  (See  Fig.  71.) 
Beginning  just  below  the  loose  ground  the  roof  and  pillars 
of  an  intermediate  level  were  carefully  and  systematically 
robbed,  thus  permitting  the  caved  ground  above  to  settle 
without  danger  of  a  crush.  This  method  of  procedure 
proved  fairly  successful  until  considerable  depth  was  reached, 
when  the  roofs  of  the  galleries  became  unsafe  and  often 
collapsed,  rendering  the  extraction  of  the  diamond-bearing 
ground  both  difficult  and  dangerous.  Could  timber  have 
been  employed  the  method  would  have  proven  much  more 
satisfactory  and  would  have  been  applicable  to  much  greater 
depths.  The  method  proved  to  be  expensive,  dangerous  and 
wasteful  and  was  superseded  by  a  form  of  sub-drift  caving. 
In  the  new  caving  system  the  method  of  opening  up  or 
developing  the  pipes  is  the  same  as  described  in  the  gal- 
lery system  of  working,  with  the  possible  exception  that 
the  intermediate  levels  or  sub-drifts  are  somewhat  further 
apart,  ranging  from  30  to  40  ft.  (See  Fig.  72.)  From  the 
main  passages  running  along  the  major  axis  of  the  deposit, 
cross-cuts  are  driven  at  3o-ft.  intervals,  being  extended  to 
the  limits  of  the  deposit.  (See  Fig.  73.)  These  cross-cuts 
are  enlarged  both  horizontally  and  vertically  by  stoping 
until  they  are  connected,  thus  forming  long  chambers  or 
stopes.  The  various  stages  of  opening  a  stope  are  shown 
in  Figs.  74  and  75.  The  roofs  of  the  intermediate  levels 
are  cut  out  by  overhand  stoping,  the  men  standing  UDOH 


2OO 


ORE  MINING  METHODS 


FIG.  74- -Elevations  and  Plans,  Showing  Method  of  Opening  Up  a.Stqpe. 

M.ELAPHYRE 

' 


FIG.  75.  —  Sketch  Showing  Plan  of  Stopes  Run  Together, 


MINING  IN  WIDE  VEINS  AND  MASSES 


201 


FIG.  76.  —  Vertical  Section  Showing  Stopes  in  Various  Stages  of  Working. 

the  broken  ground  while  drilling.  As  the  work  of  stoping 
proceeds  and  the  face  of  one  stope  recedes  from  the  wall- 
rock  another  stope  is  broken  through  from  below,  and  so 
on  until  a  number  of  stopes  are  worked,  each  level  pro- 
ceeding upward,  being  in  advance  of  the  one  below,  thus 
forming  terraces.  (See  Fig.  76.)  The  diamond-bearing 


202  ORE  MINING  METHODS 

ground  falling  upon  the  loose  ground  flows  downward  to 
the  floor  of  the  level  below,  where  it  is  shoveled  into  cars. 

The  method  of  mining  employed  in  the  diamond  mines  of 
South  Africa  is  applicable  to  large  deposits  of  considerable 
vertical  extent  and  to  ground  of  varying  degrees  of  hard- 
ness but  all  moderately  strong. 

The  advantages  of  the  method  are: 

1.  Little  or  no  timber  is  used. 

2.  Large  outputs  are  possible. 

3.  The  cost  of  mining  is  low. 

4.  Levels  can  be  placed  a  considerable  distance  apart. 

5.  Complete  extraction  of  valuable  ground. 

6.  Little  danger  from  falls  of  ground. 
The  disadvantages  of  the  method  are: 

1.  Can  be  employed  to  advantage  only  on  a  large  scale. 

2.  The  amount  of  development  is  large. 

3.  Loss  from  valuable  ground  mixing  with  waste  is  con- 
siderable at  times. 

4.  Ventilation  is  rather  complicated. 

5 .  D anger  from  mud-rushes. 

The  following  references  are  given  in  order  to  show  the  application  of  the 
various  methods  described  to  actual  mining  conditions,  rather  than  their 
theoretical  applicability  to  assumed  conditions. 

BIBLIOGRAPHY  OF  METHODS 
SQUARE-SET   MINING 

Square-Set  Mining  on  the  Comstock  Lode,  Illustrated.  Eng.  and  Mining 
Jour.,  vol.  94,  p.  746. 

Square-Set  Mining  at  Vulcan  Mines,  by  Floyd  L.  Burr.  Mines  and  Min- 
erals, vol.  32,  p.  613. 

Square-Set  Framing  at  Butte.     Eng.  and  Mining  Jour.,  vol.  96,  p.  878. 


MINING  IN  WIDE  VEINS  AND  MASSES  203 

Framing  of  Round  Timbers,  by  Percy  E.  Barbour.     Eng.  and  Mining  Jour., 

vol.  92,  p.  790. 
Top  Slicing  at  Bingham,  by  D.  W.  Jessup.     Eng.  and  Mining  Jour.,  vol. 

97,  p.  413;  also  pp.  478  and  510. 
The  Center  Star  Group  of  Mines,  Rossland,  B.  C.,  by  Roy  Hutchins  Allen. 

Eng.  and  Mining  Jour.,  vol.  89,  p.  17. 
Mining  Methods  and  Practice,  by  E.  H.  Leslie.     Mining  and  Scientific 

Press,  vol.  108,  p.  43. 
The  Mount  Morgan  Mine,  Central  Queensland,  by  J.  Bowie  Wilson.     Eng. 

and  Mining  Jour.,  vol.  87,  p.  746. 

Vertical-Face  Stoping.     Eng.  and  Mining  Jour.,  vol.  98,  p.  303. 
Square  Set  Mining  at  the  Vulcan  Mines,  by  Floyd  L.  Burr.     Trans.  Lake 

Superior  Mining  Inst.,  vol.  16,  p.  144. 
Mining  Methods  at  Goldfield,  by  Claude  T.  Rice.     Eng.  and  Mining  Jour., 

vol.  92,  p.  797. 
Mining  Methods  on  the  Mesabi  Iron  Range,  by  W.  Bayliss,  E.  D.  McNeil, 

and  J.  S.  Lutes.     Trans.  Lake  Superior  Mining  Inst.,  vol.  18,  p.  133. 
The  Mesabi  Iron  Ore  Range,  by  D  wight  E.  Woodbridge.     Eng.  and  Mining 

Jour.,  vol.  79,  p.  267. 
Mitchell  Slicing  System  in  Operation  in  Arizona,  by  Clarence  L.  Larson. 

The  Mining  World,  May  6,  1911,  p.  923. 
Mining  Problems  at  Santa  Gertrudis,  Mexico,  by  W.  G.  Matteson.     Eng. 

and  Mining  Jour.,  vol.  94,  p.  547. 

Caving  System  in  Chisholm  District,  by  L.  D.  Davenport.     Eng.  and  Min- 
ing Jour.,  vol.  94,  p.  559;   also  p.  437. 
The  Method  of  Breast  Stoping  at  Cripple  Creek,  by  G.  E.  Walcott.     Eng. 

and  Mining  Jour.,  vol.  85,  p.  102. 
Copper  Mining  in  Metcalf  District,  Arizona,  by  Peter  B.  Scotland.    Eng. 

and  Mining  Jour.,  vol.  90,  p.  118. 
Development  at  the  Esperanza  Mine,  El  Oro,  Mexico,  by  W.  E    Hindry. 

Mining  and  Scientific  Press,  vol.  99,  p.  822;  also  p.  846. 
Mining  Methods  Employed  at  Cananea,  Mexico,  by  M.  J.  Elsing.    Eng. 

and  Mining  Jour.,  vol.  90,  p.  914. 
Iron  Mining  on  the  Mesabi  Range,  by  A.  L.  Gerry.     Eng.  and  Mining  Jour., 

vol.  94,  p.  693. 
The  Mount  Morgan  Mine.     Mining  and  Scientific  Press,  vol.  88,  p.  281; 

also  Eng.  and  Mining  Jour.,  vol.  96,  p.  126. 
A  Proposed  Method  of  Timbering,  by  A.  J.  Moore.    Eng.  and  Mining  Jour., 

vol.  92,  p.  543. 

Modified  Square-Set,  by  A.  J.  Moore.    The  Mining  Magazine,  vol.  5,  p.  232. 
Triangular  Timbering  in  Tonopah-Belmont  Mine.     Eng.  and  Mining  Jour., 

vol.  93,  p.  931;  Ibid  vol.  95,  p.  1090. 
Hexagonal  Stope  Set.     Eng.  and  Mining  Jour.,  vol.  95,  p.  519. 


204  ORE  MINING  METHODS 

FILLING  METHODS 

Filling  Mine  Stopes  with  Mill  Tailings,  by  W.  H.  Homer.     Eng.  and 

Mining  Jour.,  vol.  95,  p.  36. 
Some  Features  of  Mining  Operations  in  the  Homestake  Mine,  Lead,  S. 

Dakota,  by  Bruce  C.  Yates.     Mining  and  Scientific   Press,  vol.  88, 

p.  177. 
Lake  Superior  Copper  Mining:   Present  and  Future,  by  Thomas  T.  Read. 

Mining  and  Scientific  Press,  vol.  no,  p.  209. 
Stoping  without  Timbers,  by  Mark  Ehle.     Mines  and  Minerals,  vol.  28, 

p.  460. 
The  Clifton-Morenci  District  of  Arizona,  by  W.  L.  Tovote.    Mining  and 

Scientific  Press,  vol.  101,  p.  831. 
The  Copper  of  Shasta  County,  California,  by  Donald  F.  Campbell.     Mining 

and  Scientific  Press,  vol.  94,  p.  55. 
Mining  Thick  Ore  Bodies,  by  Ray  V.  Myers.     Mines  and  Minerals,  vol. 

26,  p.  407. 
Extraction  of  Ore  from  Wide  Veins  or  Masses,  by  G.  D.  Delprat.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  21,  p.  89. 
A  System  of  Sand-Filling  Used  on  the  Rand,  by  R.  E.  Sawyer.    Trans. 

Ins.  Mining  and  Metallurgy,  vol.  22,  p.  59. 
Sand  Filling  at  Canderella  Consolidated,  by  R.  E.  Sawyer.    Eng.  and 

Mining  Jour.,  vol.  94,  p.  1213. 
Stope  Filling  and  Caving  for  Waste,  by  Ernest  K.  Hall.     Eng.  and  Mining 

Jour.,  vol.  94,  p.  396. 
Hydraulic  Stowing  in  the  Gold  Mines  of  the  Witwatersrand,  by  B.  C. 

Cullachsen.     Mining  and  Scientific  Press,  vol.  109,  p.  801. 
Butte  Back-Filling  Stoping  Method.     Eng.  and  Mining  Jour.,  vol.  96,  p.  594. 
Bore-Hole  System  of  Sand  Filling  on  the  Rand.     Eng.  and  Mining  Jour., 

vol.  97,  p.  905. 

Room  and  Pillar  Mining  at  Ray.    Eng.  and  Mining  Jour.,  vol.  97,  p.  1147. 
Cut  and  Fill  Method  in  Wide  Orebody.     Eng.  and  Mining  Jour.,  vol.  97, 

P-  514- 

Filling  Old  Open  Stopes.     Mining  and  Scientific  Press,  vol.  99,  p.  98. 
The  Panel  System  as  Applied  to  Metal  Mining,  by  H.  E.  West.     Eng. 

and  Mining  Jour.,  vol.  87,  p.  1177. 
Stoping  at  Homestake  Mine  of  South  Dakota,  by  John  Tyssowski.    Eng. 

and  Mining  Jour.,  vol.  90,  p.  74. 
Shrinkage  Stoping  on  the  Rand,  by  G.  Hildrick  Smith.    Mining  Mag., 

vol.  4,  p.  145. 
Transvaal    Gold  Mining  —  Present  and  Future  Methods,  by  F.  H.  Hatch. 

Engineering  Magazine,  vol.  45,  p.  505. 


MINING  IN  WIDE  VEINS  AND  MASSES  205 

The  Compression  of  Stope  Fillings,  by  B.  J.  Oberhausen.     School  of  Mines 

Quarterly,  vol.  26,  p.  271. 
Mining  and  Stoping  Methods  in  the  Coeur  d'Alene,  by  John  Tyssowski. 

Eng.  and  Mining  Jour.,  vol.  90,  p.  452. 
Equipment  and  Methods  at  the  Hecla  Mine,  by  Roy  H.  Allen.    Eng.  and 

Mining  Jour.,  vol.  89,  p.  311. 

Dry- Wall  Filling  Method 

Views  of  Filling  System  at  the  Baltic  Mine,  Michigan.  Trans.  Lake  Su- 
perior Mining  Inst.,  vol.  12,  opposite  pp.  no  and  in. 

Michigan  Copper  Mining  Methods,  by  Lee  Fraser.  Mining  and  Scientific 
Press,  vol.  96,  p.  847. 

Baltic  Method  of  Mining,  by  Claude  T.  Rice.  Eng.  and  Mining  Jour., 
vol.  93,  p.  897. 

Filling  Methods  at  Sudbury,  by  W.  R.  Crane.  Eng.  and  Mining  Jour., 
vol.  91,  p.  1204. 

Building  Drywalls,  Sudbury  District,  by  Albert  E.  Hall.  Eng.  and  Mining 
Jour.,  vol.  97,  p.  949. 

Mining  Methods  at  Passagem,  by  A.  J.  Bensusan.  Mining  Magazine, 
vol.  3,  P-  379- 

THE   CAVING   SYSTEMS 

Evolution  of  Caving  Systems,  by  F.  W.  Sperr.  Mines  and  Methods, 
March  1910,  p.  253. 

Sub-Drift  and  Sub-Level  Methods 

Mining  Methods  on  the  Missabe  Iron  Range,  by  W.  Bayliss  and  others. 

Trans.  Lake  Superior  Mining  Inst.,  vol.  18,  p.  133. 
Mining  on  the  Gogebic  Range,  by  P.  S.  Williams.     Mines  and  Minerals, 

vol.  31,  p.  712. 
Caving  System  at  Ohio  Copper  Mine,  by  Clarence  G.  Bamberger.    Eng.  and 

Mining  Jour.,  vol.  93,  p.  701. 
Montreal  Iron  Mine,  Gogebic  Range,  by  Geo.  E.  Des  Rochus.    Eng.  and 

Mining  Jour.,  vol.  95,  p.  955. 

Diamond  Mining,  by  Wm.  Taylor.     Mines  and  Minerals,  vol.  28,  p.  267. 
Brown  Hematite  Mining  in  Virginia,  by  Charlton  Dixon.    Mines  and 

Minerals,  vol.  32,  p.  553. 

Caving  System  in  Chisholm  District,  by  L.  D.  Davenport.    Eng.  and  Min- 
ing Jour.,  vol.  94,  pp.  511  and  437. 
Mining  on  the  Penokee-Gogebic  Range,  by  Byron  G.  Best.    The  Mining 

World,  June  17,  1911,  p.  1237. 


206  ORE  MINING  METHODS 

Iron  Mining  on  the  Mesabi  Range,  by  A.  L.  Gerry.    Eng.  and  Mining  Jour., 

vol.  94,  p.  693. 

Caving  System  of  Mining  in  America.     Eng.  and  Mining  Jour.,  vol.  94,  p.  245. 
Caving  System  at  the  Ohio  Copper  Mine,  by  F.  Sommer  Schmidt.     Mining 

and  Scientific  Press,  vol.  no,  p.  361. 
Methods  of  Iron  Mining  in  Northern  Minnesota,  by  F.  W.  Denton.     Trans. 

Am.  Inst.  Mining  Engrs.,  vol.  27,  p.  344. 
Mining  at  Miami,  Arizona,  by  R.  L.  Herrick.     Mines  and  Minerals,  vol. 

30,  p.  7Si. 

Mining  Methods  at  the  Magpie  Iron  Mines,  by  A.  Hasselbring.     Bull. 

No.  59,  Canadian  Mining  Inst.,  Mar.  1917,  p.  261. 
Notes  on  Caving  System  in  Northern  Iron  Mines,  by  Albert  H.  Fay.     Eng. 

and  Mining  Jour.,  vol.  88,  p.  961. 
The  Caving  System  on  the  Menominee  Range,  by  Reginald  Meeks.     Eng. 

and  Mining  Jour.,  vol.  84,  p.  99. 
Underground  Methods  on  the  Gogebic  Range,  by  Percival  S.  Williams.     The 

Mining  World,  Sept.  10,  1910,  p.  451. 
The  Miami  Copper  Mine,  Arizona,  by  R.  L.  Herrick.     Mines  and  Minerals, 

vol.  30,  p.  80. 
Marquette-Range  Caving  Method,  by  H.  H.  Stock.     Mines  and  Minerals, 

vol.  30,  p.  193. 
Mines  and  Mill  of  the  Consolidated  Mercur  Company,  by  Roy  Hutchins 

Allen.     Eng.  and  Mining  Jour.,  vol.  89,  p.  1273. 
Cananea  Caving   and   Slicing   Systems,  by  R.  L.  Herrick.     Mines  and 

Minerals,  vol.  30,  p.  23. 
Top-Slicing  Mining  Methods  at  Cananea,  Mexico,  by  Courtney  De  Kalb. 

Mining  and  Scientific  Press,  vol.  101,  p.  230. 
Top-Set  Slicing  in  the  Chisholm  District,  by  L.  D.  Davenport.    Eng.  and 

Mining  Jour.,  vol.  95,  p.  276;   also  p.  950. 
Top  Slicing  at  the  Caspian  Mine,  by  Wm.  A.  McEachern.     Mines  and 

Minerals,  vol.  32,  p.  733;    also  Trans.  Lake  Superior  Mining  Inst., 

vol.  16,  p.  239. 
Mining  Methods  Employed  at  Cananea,  Mexico,  by  M.  J.  Elsing.    Eng. 

and  Mining  Jour.,  vol.  90,  pp.  914,  963. 
Outline  of  Mesabi  Top-slicing  Method,  by  E.   D.   McNeil.     Eng.   and 

Mining  Jour.,  vol.  96,  p.  578. 
Top  Slicing  at  Bingham,  by  D.  W.  Jessup.     Eng.  and  Mining  Jour.,  vol. 

97,  pp.  413,  478,  510. 
Mining  and  Reduction  of  Ely  Ores,  by  R.  L.  Herrick.     Mines  and  Minerals, 

vol.  29,  p.  22. 
The  Southern  Arizona  Copper  Fields,  by  C.  F.  Tolman,  Jr.,  Mining  and 

Scientific  Press,  vol.  99,  p.  390. 


MINING  IN  WIDE  VEINS  AND  MASSES  207 

The  Copper  of  Shasta  County,  California,  by  Donald  F.  Campbell.     Mining 

and  Scientific  Press,  vol.  94,  p.  55. 

Mercur  Mining  Methods,  by  G.  H.  Dern.     Mines  and  Minerals,  vol.  25,  p.i. 
Top  Slicing  at  Bingham,  by  D.  W.  Jessup.     Eng.  and  Mining  Jour.,  vol. 

97,  P-  413- 
Copper  Mining  in  Metcalf  District,  Arizona,  by  Peter  B.  Scotland.     Eng. 

and  Mining  Jour.,  vol.  90,  p.  118. 
Diamond  Mining  at  De  Beers.    Jour.  Chem.  Metallurgical  and  Mining 

Soc.  of  South  Africa,  vol.  7,  p.  227. 
Mining  Methods  at  Kimberly,  by  John  T.  Fuller.     Eng.  and  Mining  Jour., 

94,  p.  887. 
Mining  Methods  and  Practice,  by  E.  H.  Leslie.     Mining  and  Scientific 

Press,  vol.  108,  p.  43. 
The  Caving  System  at  the  Darien  Mine,  by  A.  B.  Chase.     Mining  and 

Scientific  Press,  vol.  95,  p.  238. 

Block-Caving 

Block   Caving  as   Employed  at   the  Boston  Consolidated.     Mining  and 

Scientific  Press,  vol.  98,  p.  555. 
The  Caving  System  of  Mining,  by  W.  H.  Storms.     Mining  and  Scientific 

Press,  vol.  93,  p.  48. 
Development  at  the  Esperanza  Mine,  El  Oro,  Mexico,  by  W.  E.  Hindry. 

Mining  and  Scientific  Press,  vol.  99,  pp.  822  and  846. 
Mining  Bingham  Porphyry.     Mines  and  Methods,  Sept.  1909,  p.  12. 
Block  Caving  and  Sub  Stope  System  at  the  Tobin  Mine,  Crystal  Falls, 

Michigan.     Trans.  Lake  Superor  Mining  Inst.,  vol.  16,  p.  218. 
The  Clifton-Morenci  District  of  Arizona,  by'  W.  L.  Tovote.     Mining  and 

Scientific  Press,  vol.  101,  p.  831. 
Copper  Deposits  of  Globe-Kelvin  District,  by  Edwin  Higgins.     Eng.  and 

Mining  Jour.,  vol.  89,  p.  813. 

The  Miami-Inspiration  Ore-Zone,  by  C.  F.  Tolman,  Jr.     Mining  and  Sci- 
entific Press,  vol.  99,  p.  646. 
Los  Pilares  Mine,  by  Edward  M.  Robb,  Jr.    Mines  and  Minerals,  vol.  31, 

p.  106. 


CHAPTER  VII 

OPEN    CUT    MINING 

INTRODUCTION 

THE  surface  working  of  ore  deposits  is  confined  to  out- 
crops of  veins  and  orebodies  with  little  or  no  cover.  It 
may  be  considered  as  the  initial  or  preliminary  method  of 
extracting  ore  from  such  deposits,  and  is  at  the  same  time 
an  inexpensive  and  rapid  method  of  procedure.  Unless 
especially  advantageously  situated,  as  on  the  side  of  a  con- 
siderable elevation  or  mountain,  where  the  deposit  can  be 
attacked  at  different  levels,  the  work  of  open  cut  mining  is 
limited  to  comparatively  shallow  depths.  Depths  of 
several  hundred  even  up  to  500  ft.  have,  however,  been  at- 
tained. The  Swedish  iron  mines  have  depths  of  400  and 
500  ft. ;  the  diamond  mines  of  Kimberly,  South  Africa,  were 
some  400  ft.  deep  when  open  cut  work  was  abandoned;  the 
Tilly  Foster  iron  mine  was  worked  to  a  depth  of  over  300 
ft.;  the  Iron  Mountain  Mine  of  Missouri  reached  a  depth 
of  150  ft.  before  being  abandoned;  the  Rio  Tinto  mines 
of  Spain  are  very  extensive  both  as  to  depth  and  lateral 
extent;  the  slate  quarries  of  Wales  have  reached  a  depth  of 
600  ft. ;  etc.  Many  other  instances  of  deep  open  cut  mining 
might  be  mentioned,  such  as  the  Homestake  mines,  South 
Dakota,  and  the  Alaska-Tread  well  mines  of  Douglas 

Island,   Alaska,   but   these   mines  may  be   considered   as 

208 


OPEN   CUT  MINING  209 

having  passed  the  stage  of  open  cut  work  inasmuch  as  the 
ore  is  not  removed  directly  from  the  surface  excavation,  ex- 
cept to  a  very  limited  extent,  but  is  drawn  off  underground 
through  the  mine  workings. 

The  extension  of  the  surface  working  of  ores  to  great 
depths  by  combining  such  work  with  the  underground 
operations  has  led  to  the  employment  of  a  most  interesting 
and  important  method,  namely,  '  Glory-hole'  mining. 

The  methods  of  open  cut  mining  that  are  more  or  less 
extensively  employed  in  the  extraction  of  ore  and  similar 
materials  may  be  grouped  under  the  following  heads: 
surface  mining  by  hand;  surface  mining  by  scrapers;  open 
cut  mining  by  steam  shovels,  and  the  milling  method.  As 
outlined  above  the  methods  of  open  cut  mining  are  dis- 
cussed not  in  order  of  importance,  but  rather  in  the  order  of 
their  development  and  the  extent  and  complexity  of  opera- 
tions. Stripping  and  mining  by  hand  and  scrapers  are 
confined  largely  to  working  coal  outcrops  and  superficial 
deposits,  while  steam  shovel  work  and  the  milling  methods 
are  employed  on  a  large  scale  in  mining  both  base  and  pre- 
cious metals. 

While  it  is  the  purpose  of  this  work  to  discuss  methods 
of  mining  of  ores,  yet  it  seems  advisable  and  almost  neces- 
sary in  this  connection  to  refer  to  the  working  of  certain 
non-metalliferous  materials  in  order  to  properly  illustrate 
the  methods  as  outlined  above.  This  is  particularly  true 
of  surface  work  by  hand  and  scrapers,  although  practically 
all  ores  are,  in  certain  localities,  mined  in  a  limited  way  by 
such  methods. 


210  ORE  MINING  METHODS 

SURFACE  MINING  BY  HAND 

Wherever  large  veins  and  masses  of  workable  ore  occur 
at  the  surface,  or  with  a  thin  cover  of  barren  material  or 
wash,  it  is  customary  to  employ  some  method  of  surface 
working,  the  extent  of  such  operations  depending  upon  the 
size  of  the  deposit.  With  veins  especially,  the  amount  of 
ore  is  usually  rather  limited  or  the  position  of  the  deposit 
is  such  as  to  preclude  any  but  hand  work.  On  the  other 
hand  massive  deposits  of  low-grade  ore  or  certain  non- 
metalliferous  materials  may  be  worked  to  advantage  by 
hand.  The  mining  of  shale  for  use  in  the  manufacture  of 
Portland  cement  is  shown  in  Fig.  77.  The  shale  beds 
are  loosened  by  hand  drilling  and  blasting,  the  broken-up 
shale  being  loaded  into  carts  and  wagons  and  hauled  some 
distance  to  the  plant. 

The  application  of  hand  work  to  a  large  outcrop  of  work- 
able ore  may  be  illustrated  by  a  common  method  of  work- 
ing a  bank  of  iron  ore  which  is  to  be  loaded  into  railroad 
cars  for  transference  to  some  distant  point.  The  railroad 
track  having  been  established  at  a  certain  level,  a  dock  is 
built  up,  provided  no  excavation  is  necessary  for  bringing 
the  track  to  the  deposit,  otherwise  it  could  be  employed  to 
advantage  as  a  dock.  The  height  of  the  dock  should  be 
such  that  hand  cars  can  be  dumped  from  it  into  the  rail- 
road cars  below.  Upon  the  dock  a  series  of  hand-car  tracks 
are  laid  practically  parallel  to  each  other  and  normal  to 
the  face  of  the  bank  of  ore  to  be  excavated  and  to  the  track 
serving  the  dock.  The  bank  is  blasted  down  and  the  ore 


OPEN  CUT  MINING 


211 


•a 

nJ 
PQ 
bfl 

I 


212  ORE  MINING   METHODS 

loaded  by  hand  into  the  small  hand  cars,  which  operate 
back  and  forth  between  the  bank  and  the  dock,  the  grade 
of  the  tracks  being  slightly  in  favor  of  the  loaded  cars. 
In  this  manner  a  number  of  railroad  cars  can  be  loaded  at  one 
and  the  same  time,  and  until  the  face  of  the  bank  has  receded 
to  a  point  some  distance  from  the  dock,  large  outputs  at  low 
cost  are  possible. 

Hand  work  has  its  widest  application  in  earth  excava- 
tion or  the  working  of  other  more  or  less  soft  and  easily 
broken-up  materials,  in  the  working  of  which  it  has 
reached  its  greatest  utility.  High  banks  of  earth  are 
formed  into  terraces  sufficiently  wide  for  wagons  or  cars  to 
operate  upon  and  of  such  a  height  as  to  permit  the  control 
of  the  loosened  material.  The  faces  of  the  terraces  are 
attacked,  being  divided  into  sections  by  vertical  cuts  and 
undermined  by  horizontal  cuts  made  at  the  bottom  of  the 
bank  or  terrace.  The  remaining  outstanding  portions  of  the 
bank  are  then  broken  down,  by  bars,  a  line  of  holes  being 
made  along  the  top  of  the  bank  parallel  with  the  edge  and 
connecting  the  vertical  cuts.  Large  masses  of  the  bank 
are  thus  broken  down,  and  in  the  fall  to  the  level  below 
are  readily  broken  into  a  convenient  size  for  shoveling. 
While  rock  and  ore  formations  differ  somewhat  from  earth 
and  other  similar  materials,  yet  the  same  general  method 
of  procedure  is  applicable.  Terraces  are  usually  formed 
upon  which  the  men  stand  while  drilling  holes,  explosives 
being  used  in  breaking  down  the  face  of  the  banks.  Large 
or  mammoth  blasts  may  be  employed  in  breaking  down 
high  banks,  which  necessitate,  however,  considerable  pre- 


OPEN  CUT  MINING 


213 


paratory  work  in  the  shape  of  drilling  or  tunneling  and 
placing  and  preparing  the  blasts. 

The  application  of  open  cut  work  to  the  quarrying  of  rock 
is  shown  in  Figs.  78  and  79,  the  figures  showing  the  condition 


FIG.  78.  —  Quarry  Showing  Bench  before  Blast. 

of  the  bank  before  and  after  firing  a  large  charge  of  ex- 
plosives. 

In  the  present  day  of  keen  competition  and  large-scale 
operations  all-hand-work,  i.e.,  breaking  down  the  ore  and 
loading  by  hand,  is  fast  becoming  a  thing  of  the  past,  al- 
though it  is  still  used  in  many  localities,  as  in  the  soft-iron 
mines  of  Alabama,  where  the  ore  is  easily  handled  and  labor 
is  cheap. 


214  ORE  MINING  METHODS 

Surface  mining  by  hand  is  applicable  to  moderate-sized 
and  large  deposits  occurring  without  a  cover  or  with  covers 
of  limited  thickness.  While  hard  and  soft  materials  can 
be  handled,  a  material  that  will  break  up  into  moderately 


FIG.  79.  —  Quarry  Showing  Result  of  Blast. 

small  pieces  is  preferable,  as  it  is  more  readily  loaded  into 
cars  or  wagons  by  shovel. 

The  advantages  of  hand  work  in  open  cuts  are: 

1.  The  expenditure  for  equipment  is  slight. 

2.  There  is  little  depreciation  of  equipment  either  when 
the  mine  is  operating  or  when  it  is  closed. 

3.  Unskilled  labor  may  be  largely  employed. 


OPEN  CUT  MINING  215 

4.  May  serve  to  furnish  means  to  carry  on  development. 

5.  Removal  of  overburden  is  expensive,  so  cover  should 
be  thin. 

The  disadvantages  of  the  method  are: 

1.  Cost  of  mining  is  comparatively  high. 

2.  Operations  limited  to  relatively  small  outputs. 

3.  Owing  to  the  number  of  men  employed  the  method 
is  more  subject  to  interference  through  labor  trouble. 

SURFACE  MINING  BY  SCRAPERS 

The  use  of  scrapers  naturally  follows  hand  work  in  excava- 
tion, being  applied  to  operations  of  considerably  greater  ex- 
tent, but  is  limited  to  earthy  and  moderately  soft  materials. 
Drag  scrapers  are  extensively  employed  in  small-scale 
stripping  operations,  where  the  formations  overlying  coal 
beds  or  other  valuable  materials  consist  of  earth,  clays, 
sand  and  gravel,  shales  or  other  material  readily  loosened  by 
pick,  plow  or  small  charges  of  powder.  The  work  of  strip- 
ping off  the  overburden  is  usually  begun  at  the  point  where  it 
is  the  thinnest,  which  is  on  or  next  to  the  outcrop.  Out- 
crops usually  occur  on  hillsides,  on  the  banks  of  streams, 
etc.,  where  the  materials  excavated  can  readily  be  disposed 
of  at  a  lower  level. 

Strip-pits  formed  by  scrapers  are  45  to  60  ft.  wide  and 
vary  in  length  from  125  to  200  ft.  Larger  sized  pits  cannot 
be  worked  to  advantage  unless  wheeled  scrapers  are  em- 
ployed, owing  to  too  much  time  being  lost  in  taking  and 
discharging  the  relatively  small  loads.  Thickness  of  cover 
up  to  8  and  12  ft.  can  be  removed  quickly  and  cheaply 


2l6 


ORE  MINING  METHODS 


while  banks  of  16  even  up  to  25  ft.  are  occasionally  worked. 
It  is  doubtful  whether  it  pays  under  ordinary  circumstances 
to  strip  an  overburden  exceeding  16  ft.  in  thickness;  how- 
ever, all  depends  upon  the  character  and  amount  of  the 
material  uncovered.  A  thick  stratum  of  coal  of  good 


FIG.  80.  —  Stripping  Coal  by  Scrapers. 

quality,  a  good  bed  of  phosphate  rock,  gypsum  or  soft-iron 
ore  may  warrant  extensive  stripping  operations,  but  if  of 
considerable  lateral  extent,  more  economical  methods  should 
be  resorted  to  in  preparing  for  its  extraction. 

Stripping  operations  as  employed  in  uncovering  a  40-in. 
coal  stratum  are  shown  in  Fig.  80.  The  width  and  length 
of  the  pit  are  shown  to  good  advantage,  also  the  sloping 


OPEN  CUT  MINING  217 

ends  or  entrances  to  the  pit,  a  wagon  road  being  cut  to 
lower  grade  at  both  ends  leading  into  the  pit  to  admit 
wagons  by  which  the  coal  is  hauled  out.  The  waste  or 
waste-bank  is  shown  to  the  left.  The  coal  having  been  re- 
moved, the  resulting  excavation  serves  as  a  receptacle  for 
the  new  waste-bank  formed  by  opening  up  another  pit  to 
one  side  of  and  adjacent  to  the  previous  one. 

Water  when  it  occurs  in  considerable  quantities  is  one  of 
the  most  serious  problems  to  be  dealt  with  in  stripping,  as 
natural  drainage  cannot  always  be  effected.  Steam  pumps 
are  employed  in  the  larger-scale  work,  while  endless-belt 
pumps  driven  by  horsepower  are  commonly  used  in  freeing 
small  pits  of  excess  of  water.  A  belt  pump  is  shown  upon 
the  bank  to  the  right  of  the  pit,  Fig.  80. 

The  size,  both  width  and  length,  of  stripping  pits  may  be 
materially  increased  by  the  use  of  wheeled  scrapers,  which 
take  larger  loads  and  can  travel  greater  distances  to  the 
waste-bank  with  less  loss  of  time  than  can  the  drag  scrapes. 

Surface  work  with  scrapers  is  especially  applicable  to 
deposits  of  large  lateral  extent  and  therefore  to  bedded 
deposits.  In  fact  the  method  is  practically  limited  to 
stripping  operations,  as  in  coal,  phosphate  and  gypsum 
mining. 

The  advantages  of  scraper  work  are : 

1.  Little  equipment  needed  besides  scrapers  and  plows. 

2.  Small  force  required. 

3.  Capacity  moderately  large. 

4.  Cost  of  mining  comparatively  low. 

5.  Unskilled  labor  may  be  employed. 


2l8 


ORE  MINING  METHODS 


The  disadvantages  of  the  method  are: 

1.  Overburdens  exceeding  16  to  18  ft.  cannot  be  econom- 
ically removed  unless  the  waste  can  be  stored  close  at  hand. 

2.  Wear  of  scrapers  excessive. 

OPEN  CUT  MINING  BY  STEAM  SHOVEL 
The  advent  of  the  steam  shovel  into  mining  operations 
has  meant  much  to  the  industry,  and  it  is  largely  due  to  its 


6900 


<  ^**-*   <  *•  *  "i* 

..€.  *    *  t  * 


FIG.  81.  —  Section  across  Bingham  Canyon,  Showing  Beginning  of  Steam-Shovel 
Work  in  Stripping  Capping. 

extensive  employment  that  the  cost  of  mining  of  iron  ores 
has  been  reduced  to  an  amazingly  low  figure.  Probably  the 
most  extensive  field  of  operation  for  steam  shovels  is  in  the 
large  open  cut  iron  mines  of  Michigan  and  Minnesota,  although 
very  extensive  steam-shovel  work  is  being  done  in  the  Bing- 
ham Canyon  copper  mines,  similar  mines  at  Ely,  Nevada, 
and  in  the  Granby  mines,  British  Columbia.  (See  Fig.  81.) 


OPEN  CUT  MINING  219 

Prior  to  the  application  of  steam-shovel  work  to  the  min- 
ing of  ore  the  overburden  must  be  removed.  This  is  done 
by  steam  shovels,  the  barren  material  being  loaded  into 
railroad  cars  or  other  cars  of  several  tons'  capacity.  When 
removed  by  small  cars  they  are  usually  transferred  to  the 
waste-bank  by  an  engine  plane  or  some  form  of  rope  haulage. 
An  overburden  ranging  up  to  40  ft.  or  more  in  thickness  is 
not  uncommon,  and  while  greater  thicknesses  might  be 
removed  without  reaching  a  prohibitive  figure  from  the 
standpoint  of  costs,  yet  it  means  that  the  underlying  body 
of  ore  must  be  both  thick  and  of  high  grade.  The  thickness 
of  cover  considered  permissible  to  remove  depends  largely 
upon  its  character,  i.e.,  if  soft  or  easily  broken  the  maximum 
economic  thickness  may  be  taken,  while  hard  stratified 
formations  may  reduce  the  thickness  to  a  few  feet  and  may 
even  preclude  the  employment  of  surface  methods  alto- 
gether. The  iron  deposits  of  the  Lake  Superior  region  are 
covered  with  glacial  drift  which  is  easily  and  cheaply  re- 
moved; considerable  thicknesses  extending  over  many  acres 
are  systematically  stripped  off  and  hauled  from  the  site  of 
the  mine.  (For  work  in  Alabama  mines  see  Fig.  82.) 

There  are  three  general  methods  of  steam-shovel  work ; 
which  will  be  employed  in  a  given  case  depends  upon  exist- 
ing conditions.  Lateral  extent,  elevation  with  respect  to 
the  surrounding  country,  amount  of  overburden,  and  depth 
to  which  the  deposit  extends  are  controlling  factors  in  the 
choice  of  methods  of  procedure  in  opening  up  and  working 
a  steam-shovel-operated  mine.  The  deposit  having  been 
definitely  located  by  test  pits  and  drill  holes  and  the  over- 


220 


ORE  MINING  METHODS 


OPEN  CUT  MINING  221 

burden  removed  from  the  area  in  which  mining  is  to  begin, 
the  work  of  opening  up  the  deposit  is  begun.  The  initial 
opening  may  be  in  the  form  of  a  cut  extending  through  the 
middle  of  the  deposit  or  along  one  side,  whichever  seems 
more  advisable  from  the  standpoint  of  maintaining  grades. 
If  an  opening  is  made  through  the  middle  of  the  deposit,  the 
work  of  cutting  out  the  ore  may  be  carried  on  laterally  in 
both  directions,  while  if  done  on  one  side  it  will  have  to  pro- 
ceed in  one  direction  only.  Again,  and  in  a  similar  manner, 
a  deposit  may  be  opened  by  running  a  spiral  cut  partly 
in  the  orebody  and  working  radially  inward  and  outward, 
or  the  deposit  may  be  attacked  and  encircled  by  the  cut, 
the  removal  of  the  ore  proceeding  inward  to  the  center  of 
the  deposit.  In  either  case,  where  a  spiral  cut  is  made,  the 
ultimate  form  of  the  deposit  is  a  pit,  the  lowest  portion 
being  reached  by  spiral  tracks  upon  which  the  steam  shovels 
and  ore  trains  operate.  The  coils  of  the  spiral  are  con- 
stantly widening  as  slices  are  removed  from  the  faces  of  the 
banks  or  terraces.  Care  must  be  taken  to  maintain  the 
proper  grade  on  the  spiral. 

Ores  specially  suited  to  steam-shovel  work  should  be  soft 
or  at  least  easily  broken  up  by  moderate  charges  of  powder 
which  are  placed  in  advance  of  the  steam-shovel  work.  The 
shovel  stands  next  to  the  bank  from  which  it  takes  its  load, 
removing  a  slice  or  cut  of  6  or  8  ft.  in  width  and  depositing 
the  excavated  ore  in  the  railroad  cars  standing  on  the  track  to 
one  side  of  the  shovel.  A  cut  having  been  made  of  a  size 
to  accommodate  a  steam  shovel  and  line  of  track  for  the 
cars  serving  the  shovel,  another  cut  may  be  opened  to  one 


222  ORE  MINING  METHODS 

side,  or  in  the  middle  of  the  cut.  A  series  of  levels  is  thus 
formed,  giving  the  excavation  a  stepped  or  terraced  form. 
A  large  number  of  points  of  attack  are  thus  made  possible, 
increasing  the  capacity  of  the  mine  and  reducing  the  cost 
of  mining  by  getting  the  most  out  of  the  equipment. 

Still  another  method  of  steam-shovel  work  is  that  in  which 
the  shovel  operates  at  the  bottom  of  a  deep  pit  where  it  is 
employed  in  excavating  and  in  loading  mine  cars,  which  are 
run  to  the  foot  of  a  shaft  and  hoisted  to  the  surface  as  in 
underground  work.  In  this  method  the  steam  shovel  is  as- 
sembled at  the  bottom  of  the  pit,  its  chief  function  being  the 
loading  of  cars.  Hard  ores  may  be  blasted  down  and  then 
loaded  into  the  cars  by  the  steam  shovel.  While  this  method 
is  rather  limited  in  its  application,  yet  it  serves  a  useful  pur- 
pose under  certain  conditions  of  ore  occurrences  necessitat- 
ing special  methods  of  working. 

A  not  unimportant  use  to  which  the  steam  shovel  has  been 
put  is  that  of  loading  ore  from  stock  piles  where  it  is  stored 
during  the  winter  months,  traffic  being  closed.  Practically  all 
underground  operations  are  continued  throughout  the  winter, 
the  ore  raised  being  stored  in  the  stock  piles.  Further,  it  is 
not  unusual  for  ore  to  be  excavated  and  piled  up  in  the 
open  cuts  by  the  steam  shovels,  where  it  remains  frozen  until 
spring  when  it  is  loaded  in  the  railroad  cars  by  steam  shovels 
in  the  same  way  as  are  the  stock  piles  of  hand-mined  ore. 

Steam  shovels  are  also  occasionally  employed  in  excavat- 
ing materials  below  water  level,  as  in  mining  phosphates  in 
the  Southern  states.  In  such  work  it  is  necessary  to  operate 
the  shovel  on  solid  ground,  which  is  accomplished  by  strip- 


OPEN  CUT  MINING  223 

ping  the  deposit  and  then  employing  a  steam  shovel  with  a 
' broken'  boom,  i.e.,  a  boom  in  the  shape  of  an  inverted  V, 
the  dipper  being  supported  by  the  outer  and  downward 
sloping  part.  Further,  the  dipper  faces  toward  the  shovel 
and  takes  its  load  inward  rather  than  outward.  By  this 
arrangement  the  shovel  is  required  to  operate  backward, 
but  always  upon  the  solid,  unexcavated  bed  of  phosphates. 
The  dipper  takes  its  load  partially  under  water,  but  dis- 
charges it  into  cars  standing  on  a  track  to  one  side  of  that 
upon  which  the  shovel  operates  and  usually  at  a  higher  level. 

The  combination  of  steam-shovel  mining  with  improved 
methods  of  extraction  of  metals  from  low-grade  ores  will 
make  possible  the  opening  up  and  successful  working  of 
many  large  deposits  which  are  at  present  unworkable. 
The  steam  shovel  has  already  in  many  cases  been  an  im- 
portant factor  in  reducing  the  cost  of  mining  cheap  ores  and 
has  thus  made  a  market  for  them. 

The  use  of  steam  shovels  is  applicable  to  massive  deposits 
of  a  wide  range  in  hardness,  although  those  ores  that  break 
up  readily  are  the  best  suited  to  the  work. 

The  advantages  of  steam-shovel  work  are: 

1.  Large  outputs. 

2 .  Low  mining  costs. 

3.  Railroad  cars  may  be  loaded  directly,  thus  reducing 
cost  of  handling. 

4.  Thick  overburdens  can  be  removed  economically. 
The  disadvantages  of  the  method  are: 

1.  Expenditure  for  equipment  rather  high. 

2.  Rate  of  depreciation  high. 

3.  Skilled  labor  required  for  handling  shovels. 


224  ORE  MINING  METHODS 

THE  MILLING  METHOD 

That  particular  application  of  open  cut  mining  known  as 
the  milling  method  is  in  reality  a  combination  of  open  cut 


FIG.  84.  —  The  Method  Illustrated  Here  Is  Known  as  the  Stull-Room-Milling 
Method  and  Is  Given  in  This  Connection  to  Make  More  Understandable  the 
Open-pit  Milling  Method.  (Modeled  after  Sketch  by  F.  W.  Denton.) 

and  underground  work,  or,  more  strictly  speaking,  mining  in 
an  open  cut  and  handling  the  ore  underground.     Owing  to 


OPEN  CUT  MINING  225 

the  successful  application  of  the  milling  method  as  origi- 
nally employed  in  surface  work,  it  is  now  being  extended  to 
underground  work,  where  it  is  also  meeting  with  marked 
success,  in  certain  instances  at  least.  (See  Fig.  83.) 

The  milling  method  is  underhand  stoping  applied  to 
large  deposits,  the  work  of  cutting  out  the  ore  being  con- 
fined to  limited  areas  around  the  mouths  of  raises  or  winzes. 
In  developing  a  deposit  to  be  worked  by  the  milling  method 
it  is  essential  that  the  haulageways  on  the  respective  levels 
be  so  arranged  as  to  facilitate  the  handling  of  large  quan- 
tities of  ore,  as  the  milling  method  is  productive  of  large 
tonnage.  This  can  best  be  done  by  so  arranging  the  haul- 
ageways that  the  going  and  returning  ways  are  separate, 
thus  eliminating  the  interference  of  loaded  and  empty  cars. 
Parallel,  elliptical  or  roughly  circular  systems  of  haulage- 
ways,  connected  by  cross-cuts  at  frequent  intervals  to  facili- 
tate the  movement  of  cars,  provide  ample  opportunity  for  the 
handling  of  both  loaded  and  empty  cars.  Such  development 
work  is  done  on  each  level,  but  not  necessarily  completed, 
except  on  the  upper  level,  until  the  surface  workings  have 
reached  and  destroyed  the  haulageways  on  that  level, 
when  a  similar  arrangement  of  ways  should  be  in  readiness 
for  handling  the  ore  on  the  level  below,  and  so  on,  level  by 
level,  as  the  work  progresses  downward.  (See  Fig.  83.) 

The  development  work  on  a  level  having  been  com- 
pleted, raises  are  put  up  along  the  line  of  the  haulage- 
ways  at  intervals  of  50  to  75  feet  or  more.  The  barren 
material  covering  the  orebody  should  be  removed  before 
the  raises  break  through  to  the  surface.  Chutes  for 


226 


ORE  MINING  METHODS 


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OPEN  CUT  MINING  227 

the  control  of  the  ore  and  the  loading  of  cars  are  placed 
at  the  foot  of  each  raise,  and  when  so  equipped  the  work 
of  breaking  the  ore  may  be  begun.  Drills  are  mounted 
on  tripods  at  the  edge  of  the  raises,  and  the  ore  broken  by 
the  charges  so  placed  falls  by  gravity  into  the  raises,  from 
which  it  is  drawn  into  cars  and  sent  to  the  surface.  Pits 
are  soon  formed  about  the  mouths  of  the  respective  raises, 
which  as  they  increase  in  size  provide  more  room  for  other 
groups  of  drillers.  Ultimately  the  pits  formed  along  the 
line  of  a  haulageway  run  together,  as  do  those  of  different 
lines  of  haulage,  thus  forming  a  large  pit  the  bottom  of 
which  is  composed  of  a  number  of  inverted  conical  openings 
connected  by  raises  with  the  underground  haulage  system. 
It  is  evident  that  after  the  pits  have  coalesced  the  rims  of 
the  raises  will  have  resolved  themselves  into  ridges  standing 
between  the  pits,  upon  which  ridges  the  mounting  of  drills 
is  practically  impossible. 

Further  breaking  of  ore  must  then  be  done  in  one  of 
two  ways,  namely:  the  drilling  is  done  by  hand  drillers 
operating  miscellaneously  on  the  sloping  surface  of  the  pits 
or  by  systematic  work,  beginning  at  the  bottom  of  the 
funnel-shaped  pits  and  proceeding  upward.  Sections  rang- 
ing from  a  few  up  to  10  and  12  ft.  in  thickness  are  thus 
removed  from  the  bottom  to  the  top  of  the  pits,  the  drills 
being  returned  to  the  bottom  after  each  section  is  com- 
pleted, when  work  upon  another  section  is  begun.  The 
work  of  breaking  the  ore  may  then  be  accomplished  by 
either  underhand  or  overhand  stoping,  the  former  at  the 
beginning  of  the  operations,  the  latter  after  the  milling 


228  ORE  MINING  METHODS 

pits  have  run  together  forming  one  large  open  cut.  As 
many  as  twenty  milling  pits  may  be  worked  together,  but 
probably  ten  or  thereabouts  is  a  more  usual  number. 

Those  ores  that  break  up  into  moderately  small  pieces 
are  best  suited  to  the  milling  method,  although  fairly  hard 
ores  are  worked  satisfactorily.  Care  must  be  taken  to 
insure  against  falls  of  rock  or  ore  while  the  laborers  are  at 
work  in  the  pits,  which  can  only  be  done  by  barring  down 
all  loose  rock  and  even  employing  small  charges  of  powder 
to  remove  dangerous  portions  of  the  walls. 

Steam  shovels  are  occasionally  employed  in  conjunction 
with  the  milling  method,  being  used  to  excavate  the  ore 
and  dump  it  into  the  milling  pits.  Owing  to  the  limited 
space  for  trackage  and  the  difficulty  experienced  in  properly 
arranging  and  maintaining  the  working  of  the  steam  shovels 
about  the  pits,  this  particular  phase  of  the  milling  method 
is  comparatively  little  used. 

Glory-hole  mining  is  the  milling  method  after  it  has  been 
fully  developed,  i.e.,  after  the  pits  formed  by  breaking  ore 
round  the  mouths  of  the  raises  have  run  together  and 
by  continued  work  have  reached  considerable  depth,  thus 
forming  a  large  and  deep  excavation.  Glory-hole  mining 
is  employed  in  practically  all  mines  where  large  orebodies 
occur  at  the  surface,  the  more  superficial  portions  being 
worked  by  open  cuts  operated  by  hand  and  in  many  cases 
resembling  quarrying  methods.  After  a  certain  depth  has 
been  reached  tunnels  may  be  employed  which  connect  with 
a  shaft  or  with  the  surface  at  lower  levels.  In  the  mean- 
while the  lode  will  have  been  developed  in  depth  and  raises 


OPEN  CUT  MINING  229 

put  up  which  finally  connect  with  the  bottom  of  the  open 
cut,  when  the  work  of  handling  the  ore  is  transferred  from 
the  tunnel  levels  to  the  main  levels  of  the  mine  by  way  of 
the  mill-holes.  Owing  to  the  likelihood  of  large  masses  of 
rock  and  ore  falling  into  the  mill-holes  and  choking  them, 
it  is  common  practice  to  provide  a  grizzly  of  logs  at  the 
top  of  the  raises,  thus  separating  out  the  boulders,  which 
are  reduced  to  the  proper  size  to  pass  the  grizzlies  by  sledge 
or  bull-dozing,  i.e.,  by  the  use  of  small  charges 'of  powder. 
Further,  in  order  to  prevent,  or  reduce  to  a  minimum,  the 
choking  of  the  mill-holes  it  is  often  necessary  to  change  the 
direction  of  the  holes.  Also  in  order  to  reduce  or  entirely 
eliminate  the  weight  of  the  column  of  broken  ore  standing 
in  the  mill-holes,  the  holes  may  be  offset  to  one  side  of  the 
haulageway  or  tunnel  below,  thus  requiring  less  support  to 
maintain  them. 

While  many  orebodies  are  of  fairly  uniform  value  through- 
out, there  are  others  in  which  the  values  are  very  spotted, 
the  workable  portions  coming  and  going  in  a  very  irregular 
manner.  It  is  evident,  then,  that  where  deposits  of  variable 
mineral  content  are  worked  by  the  milling  method,  especially 
in  the  large  open  cuts  where  little  or  no  discrimination  can  be 
made  between  ore  and  waste  in  breaking  down  the  walls,  all 
material  entering  the  mill-holes  must  be  taken  care  of,  which 
is  usually  done  by  sending  the  waste  to  empty  or  working 
stopes  as  filling,  while  the  ore  is  diverted  to  the  loading  chutes 
for  cars.  This  is  made  possible  by  employing  a  number  of 
mill-holes  so  arranged  that  accumulations  of  ore  or  waste  may 
be  drawn  off  alternately  through  one  or  more  of  the  holes. 


230  ORE  MINING  METHODS 

It  is  claimed  that  it  is  not  uncommon  for  two  men  to  loosen 
and  mill  as  much  as  300  and  400  tons  of  ore  per  day. 

The  name  " glory-hole"  probably  came  to  be  applied  to 
the  large  open  cuts  because  of  the  large  number  of  deaths  of 
laborers  working  in  and  about  them  —  the  victims  of  falls 
were  spoken  of  as  having  gone  to  Glory. 

As  previously  mentioned,  the  milling  method  of  mining  is 
occasionally  employed  underground,  when  it  is  often  referred 
to  as  underground  glory-hole  method.  Where  the  over- 
burden is  too  thick  for  economical  removal  and  the  deposit 
warrants  its  use  the  milling  method  may  be  employed,  the 
raises  being  put  up  to  or  close  to  the  top  of  the  orebody 
and  the  work  of  breaking  ore  begun  by  working  laterally 
and  downward.  Large  roughly  rectangular  or  circular 
stopes  or  rooms  are  thus  formed,  in  the  centers  of  which  are 
the  mill-holes  or  raises.  The  overburden  is  supported 
either  by  timbers  placed  across  the  top  of  the  stope,  usually 
in  A-form,  or,  if  the  stope  is  not  too  wide  and  the  ore  is 
sufficiently  strong  to  stand,  a  back  of  ore  several  feet  in 
thickness  may  be  left,  being  formed  into  an  arch,  thus 
doing  away  with  timber  supports.  Stopes  of  one  hundred 
or  more  feet  in  height  may  be  worked  in  this  manner,  but  a 
large  part  of  the  orebody  is  left  standing  between  the 
stopes.  If  the  mineral  is  cheap,  as  rock  salt,  this  might  be 
permitted,  otherwise  some  other  method  of  mining  should  be 
employed.  A  similar  method  has  been  employed  in  the  iron 
mines  of  the  Lake  Superior  region,  known  as  the  l  stull-room ' l 

1  The  following  description  of  the  method  by  F.  W.  Denton  occurs  in  the 
Trans.  Am.  Inst.  Mining  Engrs.,  vol.  27,  pp.  377-778. 


OPEN  CUT  MINING  231 

method,  but  has  often  to  be  supplemented  by  some  other 
method,  which  is  somewhat  difficult  to  do  owing  to  the  large 
open  stopes,  the  collapse  of  which  must  not  only  be  expected 
but  provided  for.  (See  Fig.  84.) 

Pillars  left  in  the  preliminary  working  of  a  deposit  may 
later  be  removed,  even  when  the  stopes  have  been  filled  or 
have  caved,  by  putting  up  raises  to  the  pillars  and  cutting 
them  out  by  overhand  stoping,  or  the  raises  may  be  run 
through  the  pillars,  and  by  careful  timbering  the  pillars  may 
be  removed  by  underhand  stoping.  In  a  similar  manner 
the  filling  in  stopes,  that  was  formerly  considered  too  poor 
to  work  with  profit,  but  by  improved  processes  has  been 
rendered  profitable  to  treat,  may  be  drawn  off  by  putting  up 
raises  and  tapping  the  stopes.  Great  care  must  be  taken 
in  all  of  this  work  in  order  to  control  the  caving  that  is  al- 
most sure  to  follow  the  removal  of  large  quantities  of  ma- 
terial in  comparatively  short  periods  and  in  limited  areas. 

"  The  top  of  the  room  is  first  cut  out  by  driving  a  wide 
drift  just  under  the  sand,  and  supporting  this  drift  with 
s-addle-back  timbering,  which  becomes  the  roof  of  the  room. 
This  roof-timber  is  put  in  by  driving  from  sub-drifts  on  the 
same  level,  thereby  avoiding  the  hoisting  of  timbers.  The 
rooms  could  be  started  from  the  tops  of  raises  if  necessary. 
After  the  roof  is  thus  securely  supported,  the  ore  is  stoped 
underhand,  through  the  raises,  to  the  drift  in  the  center  of 
the  bottom  of  the  room,  where  it  is  run  into  the  cars  and 
trammed  to  the  shaft.  The  sides  of  the  room  are  left  un- 
supported; and  the  doubtful  part  of  the  experiment  was, 
whether  these  sides  would  stand.  A  number  of  rooms  have 


232  ORE  MINING  METHODS 

already  been  mined  in  this  way  without  any  trouble  whatever 
and,  at  least  for  the  Fayal  deposit,  the  experiment  seems  to 
be  successful.  Many  of  the  Mesabi  deposits,  however, 
are  traversed  by  a  system  of  parallel  and  almost  vertical 
fissures  or  seams,  rilled  with  crushed  quartz  which,  while  only 
a  fraction  of  an  inch  in  thickness  as  a  rule,  would  seriously 
interfere  with  this  method.  The  Fayal  has  none  of  these 
seams,  at  least  where  the  saddle-back  rooms  have  been  made, 
and  no  trouble  has  arisen  from  caving  sides.  The  ore  ob- 
tained from  these  rooms  is  probably  the  cheapest  ore  ob- 
tained underground  on  the  Mesabi,  as  the  advantage  of 
easy  breaking  is  obtained  with  a  low  timber-cost." 

The  milling  method  is  probably  most  extensively  employed 
in  the  Michigan  and  Minnesota  iron  fields,  where  it  is  used 
both  as  a  surface  or  open  cut  method  and  underground. 
Similar  methods  are  in  use  at  the  Alaska-Treadwell  mines, 
Douglas  Island,  Alaska;  at  the  Homestake  mines,  Lead, 
South  Dakota;  in  the  gold  mines  at  Goldfield,  Nevada; 
at  the  Comstock  Lode,  Virginia  City,  Nevada;  in  the  cop- 
per mines  of  Bingham  Canyon,  Utah;  in  the  Yellow  Aster 
Mine,  Randsburg,  California;  in  the  Big  Indian  Mine, 
Helena,  Montana;  in  the  Granby  mines,  Phoenix,  British 
Columbia,  and  at  numerous  other  mines. 

The  milling  method  of  mining  is  applicable  to  large  bodies 
of  ore  either  in  veins  or  masses,  and  to  wide  ranges  in  char- 
acter of  ore.  The  method  is  elastic,  as  it  is  employed  in 
both  surface  and  underground  work. 

The  advantages  of  the  milling  method  are: 

i.  Large  outputs  per  man. 


OPEN  CUT  MINING  233 

2.  Low  mining  costs. 

3.  Much  waste  material  may  be  obtained  for  filling, 
which  is  important  if  other  methods  of  mining  are  operated 
in  conjunction  with  the  milling  method. 

4.  There  is  a  minimum  amount  of  handling  of  ore. 

5.  When  working  ground  previously  mined  in  which  con- 
siderable timber  was  used,  much  of  the  timber  can  be  picked 
from  the  ore  and  reused. 

The  disadvantages  of  the  method  are: 

1.  When  employed  as  a  surface  method  of  working,  the 
orebody  must  extend  close  to  the  surface  to  be  stripped. 

2.  Mill-holes  choke,  especially  with  ores  of  certain  char- 
acter;  ores  breaking  moderately  fine  and  granular  in  form 
without  clay  are  preferable. 

3.  Rain  and  snow  interfere  with  work  on  the  sloping 
sides  of  the  pits. 

4.  Considerable  danger  from  falls  of  men  and  rocks  and 
flying  rock  from  blasts. 

5.  When  carried  on  underground  there  is  considerable 
danger  of  caves  which  may  extend  into  the  workings. 

6.  Little  opportunity  to  sort  waste  from  ore. 
Generally  considered,  surface  or  open  cut  methods  are 

applicable  to  the  outcrops  of  large  veins  and  massive  de- 
posits occurring  at  or  within  a  few  feet  of  the  surface. 
Practically  all  kinds  of  minerals  and  ores  as  well  as  non- 
metalliferous  materials  are,  when  possible,  mined  by  open 
cuts.  Quarries  of  stone,  slates,  etc.,  are  to  all  intents  and 
purposes  open  cut  mining  operations  and  may  be  classed  as 
such. 


234  ORE  MINING  METHODS 

The  advantages  of  open  cut  mining  are: 

1.  Work  can  be  done  on  a  large  scale. 

2.  Mining  cost  is  low. 

3.  Lighting  workings  is  eliminated  or  materially  lessened. 

4.  No  timber  is  required. 

5.  Sorting  can  be  done  to  advantage. 

6.  Practically  no  danger  from  fires,  gases,  etc. 
The  disadvantages  of  open  cut  work  are: 

1.  Cost  of  real  estate  for  both  the  open  cut  and  storage 
of  waste  is  a  large  item. 

2.  The  depth  to  which  the  strictly  open  cut  work  can 
be  carried  is  limited,  although  with  the  milling  method  great 
depths  are  worked. 

3.  The  cost  increases  greatly  with  depth,  unless  connec- 
tion is  made  with  the  underground  workings  as  in  glory-hole 
work. 

4.  Danger  of  falls  of  rock  and  men. 

5.  Danger  of  inundations. 

6.  Inconvenience  of  working  in  stormy  weather. 

7.  Proper  slopes  must  be  given  to  the  sides  of  the  open 
cuts  to  prevent  walls  from  caving  —  a  slope  of  i  to  i  J  for  hard 
formations  and  i  to  3  for  clay  is  commonly  given. 

The  comparative  advantages  and  disadvantages  of  the 
various  methods  of  open  cut  work  are  as  follows : 

1.  The  outputs  of  the  milling  method  and  steam-shovel 
work  are  much  greater  per  man  than  by  hand  or  scraper 
work,  and  by  scraper  than  by  hand  work. 

2.  The  cost  of  mining  per  ton  is  much  less  with  the  mill- 
ing method  and  steam  shovel  than  with  hand  and  scraper 


OPEN  CUT  MINING  235 

work,  while  scraper  work  is  cheaper  than  hand  work,  and 
steam-shovel  work  is  cheaper  than  by  milling. 

3.  The  milling  method  can  be  used  to  advantage  in  de- 
posits too  small  for  steam  shovels  to  operate  upon. 

4.  Fewer  laborers  are  required  in  scraper  than  in  hand 
work,   and  in  steam-shovel  than  in  the  milling  method, 
but  more  skilled   labor  is  required  in  steam-shovel   and 
milling. 

5.  Less  danger  of  accidents  in  hand,  scraper  and  steam- 
shovel  work  than  in  the  milling  method,  and  more  in  hand 
and  steam- shovel  work  than  in  scraper  work. 

6.  Ores  may  be  sorted  to  better  advantage  by  hand, 
scraper  and  steam-shovel  work  than  in  the  milling  method, 
and  better  in  hand  and  scraper  than  with  steam-shovel 
work. 

BIBLIOGRAPHY  OF  OPEN   CUT  MINING 
STEAM-SHOVEL  WORK 

Engineering  Features  of  Steam  Shovel  Work  at  Bingham,  by  H.  C.  Goodrich. 

Mining  and  Scientific  Press,  vol.  103,  p.  624. 
Mining  Methods  on  the  Mesabi  Iron  Range,  by  W.  Bayliss,  E.  D.  McNeil, 

and  J.  S.  Lutes.     Trans.  Lake  Superior  Mining  Inst.,  vol.  18,  p.  133. 
The  Mesabi  Iron-Ore  Range,  by  Dwight  E.  Woodbridge.     Eng.  and  Mining 

Jour.,  vol.  79,  pp.  266  and  365. 
Mining  at  Bingham,  Utah,  by  James  W.  Abbott.     Mining  and  Scientific 

Press,  vol.  94,  p.  596. 
Open  Cut  Mining  on  the  Mesabi  Iron  Range.     Eng.  and  Mining  Jour.,  vol. 

74,  p.  302. 
The  Mesabi  Range,  by  Cyril  Brockenbury.     Mines  and  Minerals,  vol.  21, 

p.  150. 
Mining  Methods  in  the  Mesabi  Iron  District,  Minnesota,  by  Kirby  Thomas. 

Mining  and  Scientific  Press,  vol.  88,  p.  258. 
Stopes  in  Steam-Shovel  Mining,  by  E.  E.  Barker.    Mining  and  Scientific 

Press,  vol.  102,  p.  320. 


236  ORE  MINING  METHODS 

The  Utah  Copper  Mine,  by  Courtney  De  Kalb.     Mining  and  Scientific 

Press,  vol.  98,  p.  516. 
Mining  Methods  in  the  North,  by  T.  A.  Rickard.  Mining  and  Scientific 

Press,  vol.  98,  p.  382. 
Open-Pit  Mining,  by  Chas.  E.  Van  Barneveld.  Iron  Mining  in  Minnesota, 

p.  131. 

GENERAL   OPEN  CUT   WORK 

Premier  Diamond  Mine,  by  Ralph  Stokes.    The  Mining  Magazine,  vol.  7, 

p.  366. 
The  Diamond  Mines  of  South  Africa,  by  G.  F.  Williams.     Trans.  Am. 

Inst.  Mining  Engrs.,  vol.  15,  p.  392. 
Mining  Methods  on  the  Mesabi  Iron  Range,  by  W.  Bayliss,  E.  D.  McNeil, 

and  J.  S.  Lutes.     Trans.  Lake  Superior  Mining  Institute,  vol.     18, 

P-  133. 
Methods  of  Mining  Iron  Ore  at  Sunrise,  Wyoming,  by  B.  W.  Vallat.     Eng. 

and  Mining  Jour.,  vol.  85,  p.  399. 
Glory-Hole  Mining  at  De  Lamar,  Nevada,  by  W.  R.  Wardner.     Eng.  and 

Mining  Jour.,  vol.  87,  p.  451. 
Stripping  with  Drag-line  Excavators,  by  L.  E.  Ives.    Eng.  and  Mining  Jour., 

vol.  98,  p.  941. 
Open-Pit  Mining,  by  Geo.  J.  Young.     Elements  of  Mining,  Chapter  XII, 

p.  308. 


CHAPTER  VIII 
COST    OF    MINING 

INTRODUCTION 

THE  cost  of  mining  is  dependent  upon  a  number  of 
more  or  less  general  considerations,  such  as  period  and  ex- 
tent of  operations,  character  and  value  of  ore,  organization 
of  working  force,  transportation  facilities,  etc.  A  number 
of  these  factors  are  interdependent,  as  time  work  has  been 
carried  on,  extent  of  operation,  organization,  etc. ;  the  scale 
of  operation  and  organization  naturally  requires  time  for 
growth  and  perfecting.  The  same  is  true  of  transportation 
facilities,  but  probably  to  a  less  degree.  Increased  output 
made  possible  by  efficient  equipment  and  organization  is 
without  doubt  the  most  important  factor  in  reduction  of 
costs,  which  is  true  not  only  of  the  breaking  of  ore  but  of 
every  other  operation  both  above  and  below  ground.  Hard 
times  also  act  to  reduce  cost  of  working,  but  like  the  cause 
that  produces  them,  stringency  in  the  money  market,  the  con- 
ditions are  abnormal  and  are  to  be  considered  as  cause  of  tem- 
porary variations  only  and  not  as  constantly  acting  factors. 

General  Considerations.  —  Speaking  more  specifically,  the 
cost  of  mining  is  influenced  by  variations  in  width  of  vein  or 
size  of  deposit  and  value  of  ore  with  depth,  hardness  of  ore 
and  gangue  materials,  presence  of  water,  cost  of  labor  and 

supplies,  etc.     Variations  in  width  of  deposits,  the  mineral 

237 


238  ORE  MINING  METHODS 

content  remaining  the  same  per  foot  in  depth,  means  the 
handling  of  more  or  less  material  with  the  same  ultimate  re- 
turn, and  may  be  a  potent  factor  in  increasing  cost  of  work- 
ing, as  when  the  vein  is  very  narrow,  this  necessitates  the 
breaking  of  much  wall  rock,  as  in  resuing.  The  hardness  of 
the  ore  may  also  vary  considerably  with  depth  and  if 
coincident  with  reduced  mineral  content  may  result  in  a 
very  material  increase  in  cost  of  stoping. 

The  stability  of  both  vein-content  and  wall  rock,  i.e.,  the 
ability  to  stand  unsupported  in  moderate  sized  stopes,  is 
probably  of  equal  importance  with  hardness  of  the  mineral 
bearing  and  non-mineral  bearing  formations.  Weak  and 
unstable  formations  involve  the  element  of  support,  which  in 
extreme  cases  may  increase  the  cost  of  working  to  a  prohibi- 
tive figure.  By  carefully  arching  the  backs  of  the  stopes, 
stable  formations  may  be  made  to  stand  otherwise  unsup- 
ported in  stopes  50  ft.  or  more  in  width;  the  large  open 
stopes  of  the  Homestake  mines  of  South  Dakota,  and  of  the 
Alaska-Treadwell  mines,  Douglas  Island,  Alaska,  are  good 
illustrations  of  such  conditions.  On  the  other  hand  weak 
and  unstable  formations  may  be  worked  at  moderately  low 
costs  by  the  employment  of  filling  methods.  As  the  con- 
ditions existing  in  the  majority  of  the  metal  mines  of  the 
United  States  are  such  as  to  necessitate  support,  it  is  evi- 
dent that  the  cost  of  support  may  enter  into  the  expense  of 
working  and  often,  as  in  square-set  mining,  constitutes  an 
important  item  in  such  calculations. 

The  character  of  the  ore  is  of  importance,  for  if  the  whole 
vein-content  is  uniform  in  value,  the  method  of  working  the 


COST  OF  MINING  239 

deposit  will  differ  materially  from  the  case  where  the  values 
are  scattered,  occurring  possibly  in  thin  stringers  or  in 
bunches.  In  the  former  case  the  value  can  be  depended 
upon  and  will  vary  between  moderately  narrow  limits;  in 
the  latter  case  much  barren  material  will  have  to  be  mined, 
thus  necessitating  considerable  sorting  and  handling.  Fur- 
ther, in  the  latter  case  we  may  have  a  concentrating  ore 
from  which  the  waste  may  be  largely  eliminated,  in  the 
former  case  a  smelting  ore  may  be  the  result;  in  either  case 
the  subsequent  metallurgical  treatment  is  really  the  deter- 
mining factor  in  the  economical  working  of  the  deposit. 
While  it  costs  as  much  or  more  to  break  waste  as  to  break 
ore,  yet  the  tonnage  costs  are  usually  charged  to  ore  alone, 
which  is  an  important  consideration  in  figuring  costs. 

The  presence  of  water  in  considerable  quantities  does  not 
directly  influence  the  cost  of  breaking  ore;  however,  there 
are  numerous  instances  where  excessive  quantities  of  water 
are  encountered,  even  in  certain  portions  of  otherwise  mod- 
erately dry  districts,  and  in  such  cases  the  cost  of  breaking 
ore  may  run  up  to  an  abnormally  high  figure.  Aside  from 
the  inconvenience  of  working  at  a  stope  face  flooded  with 
water  or  in  a  constant  downpour  from  the  roof,  the  presence 
of  large  quantities  of  water  materially  increases  the  peril  of 
working,  increasing  the  number  of  falls  both  by  preventing 
adequate  inspection  and  by  the  tendency  to  force  off  the  frac- 
tured rock  and  ore  by  hydraulic  pressure.  Falls  of  rock  may 
be  largely  increased  by  the  action  of  water  under  pressure 
acting  in  crevices,  fault  planes  and  slips,  especially  when  an 
attempt  is  made  to  check  the  flow  by  wedging  and  pumping 


240  ORE  MINING  METHODS 

in  cement,  clay,  sawdust,  etc.,  as  was  done  in  the  Central 
Mine  of  the  Federal  Lead  Company  at  Flat  River,  Missouri. 

While  the  wages  paid  in  the  various  metal  mining  districts 
of  the  United  States  vary  considerably,  yet  the  actual  differ- 
ence in  cost  for  work  done  is  relatively  slight.  The  efficiency 
of  the  labor  depends  directly  upon  the  wage  paid,  although 
there  are  possible  exceptions,  as  under  certain  conditions 
of  labor,  location,  etc.  The  operator  then  gets  a  return 
for  his  labor  expenditure  in  proportion  to  the  amount  paid. 

The  cost  of  supplies,  such  as  fuel  for  power  purposes, 
timber  for  support,  and  tools,  steel,  explosives,  etc.,  for 
breaking  ground,  while  it  varies  considerably  in  various 
localities,  probably  does  not,  as  Finlay  has  shown,  even  with 
a  variation  of  50  per  cent  in  the  price,  produce  a  difference 
of  over  10  per  cent  in  total  current  mining  costs. 

Other  conditions  having  an  indirect  bearing  upon  the  cost 
of  mining  and  especially  breaking  ore  are:  abnormal  tem- 
perature of  the  mine  atmosphere;  presence  of  gases,  natural 
or  artificial;  dust  resulting  from  operation  of  drills;  altitude, 
etc.  High  temperature  may  be  due  to  inherent  qualities 
in  the  deposit  worked  or  to  poor  and  inadequate  ventila- 
tion. Excessive  temperatures  such  as  are  experienced  in 
the  mines  of  the  Comstock  Lode  and  a  few  other  mines  in 
the  United  States  are  not  of  sufficiently  common  occurrence 
to  warrant  consideration  in  this  connection,  but  tempera- 
tures of  75  to  90°  are  of  fairly  common  occurrence  and  are 
to  be  found  in  the  lower  levels  of  many  mines  in  this  country. 
The  deeper  mines  of  Keweenaw  Point,  Michigan;  of  the 
Butte  District,  Montana;  and  of  other  western  districts 


COST  OF  MINING  241 

may  be  cited  as  illustrations  of  mines  having  temperatures 
above  the  normal.  The  reduced  efficiency  and  effectiveness 
of  the  labor  returns,  while  apparently  inconspicuous  and 
relatively  small  considered  by  individual  units,  are  in  reality 
of  much  importance  when  the  elements  of  time  and  numbers 
are  involved.  Considered  independently  of  other  conditions 
a  few  degrees  rise  in  temperature  does  not  in  the  long  run 
have  a  deleterious  effect  upon  the  efficiency  of  labor,  but 
when  combined  with  other  conditions,  such  as  vitiated  air 
resulting  from  the  presence  of  moisture,  mine  gases  and 
powder  smoke,  may  seriously  affect  the  health  ol  the  miners 
and  decrease  the  effectiveness  of  their  labor. 

Altitude  has  a  twofold  influence  upon  labor  conditions  in 
that  it  affects  the  health  and  general  tone  of  the  individual 
effort,  and  by  its  effect  upon  climatic  conditions  may 
seriously  curtail  the  extent  and  duration  of  the  operations. 
Further,  the  operations  may  be  limited  to  certain  seasons  by 
no  other  causes  than  the  failure  of  transportation,  excessive 
rainfall  and  deep  snowfall  limiting  the  operation  of  the  rail- 
roads, and  severe  weather.  Limited  periods  of  operation  in 
turn  affect  the  labor  conditions,  requiring  high  wages  to 
maintain  the  proper  standard  of  efficiency. 

DETAILED  DISCUSSION  or  COSTS  or  MINING 

The  principal  factors  influencing  costs  of  mining  ore  have 
been  indicated  in  the  preceding  pages,  and  particularly 
those  entering  more  or  less  directly  into  the  cost  of  break- 
ing ore  or  stoping.  When  an  attempt  is  made  to  investi- 
gate the  cost  of  any  one  single  operation,  as  driving  levels, 


242  ORE  MINING  METHODS 

stoping,  etc.,  it  at  once  becomes  obvious  that  there  are 
many  difficulties  to  be  encountered.  It  is  rarely  the  case 
that  reliable  information  can  be  secured  regarding  the  cost 
of  distinctively  separate  operations,  the  tendency  in  ordi- 
nary mining  practice  and  cost-keeping  being  to  group  cer- 
tain closely  related  expenses  under  a  few  more  or  less  general 
headings,  such  as  mining,  milling,  and  smelting.  These 
may  in  turn  be  subdivided  into  other  more  specific  yet 
generalized  headings,  as  in  the  case  of  mining,  where  we  may 
have  costs  of  development,  stoping  and  handling  ore. 

While  the  cost  of  stoping  or  any  other  operation  in  mining 
may  be  specifically  stated,  yet  a  careful  differentiation  of 
expenses  between  stoping,  timbering,  handling  ore,  labor  and 
supplies  is  rarely  attempted.  The  cost  of  mining  as  usually 
given  in  published  reports  of  mining  operations  is  more  often 
misleading  than  otherwise  in  that  there  are  a  number  of 
unknown  factors  involved,  the  result  being  that  the  figures 
are  of  little  or  no  value  even  for  comparative  purposes. 

Fundamental  Items  of  Cost.  -  -  The  cost  of  mining  per  unit 
amount,  as  per  ton  or  cubic  yard,  fathom,  etc.,  when  cal- 
culated as  closely  as  possible  and  when  shorn  of  all  super- 
fluous and  extraneous  charges  may  be  considered  as  made 
up  of  the  following  items: 

1.  Cost  of  labor. 

2.  Cost  of  supplies. 

3.  Cost  of  power. 

4.  Cost  of  lighting. 

5.  Cost  of  support  in  stopes. 

6.  Cost  of  handling  ore  in  stopes. 


COST  OF  MINING  243 

The  above  considerations  apply  equally  well  to  the  vari- 
ous phases  of  mining  as  development  and  breaking  ore. 

The  first  four  items  given  above  are  costs  common  to 
mining  operations  and  are  largely  independent  of  local  con- 
ditions. The  two  last  mentioned  items  may  be  considered 
as  special  costs  in  that  they  involve  special  methods  of 
working  brought  about  by  local  conditions  and  character 
of  deposit. 

Labor.  -  -  The  wage-scale  of  a  district  is  indicative  of  both 
the  character  and  efficiency  of  the  labor.  A  difference  of  30 
cents  per  hour  (range  20  to  50  cents  in  the  United  States) 
may  be  and  is  usually  largely  due  to  the  quantity  and  quality 
of  labor  available.  In  this  connection  the  question  might 
properly  be  raised  as  to  what  constitutes  a  day's  work. 
Aside  from  the  element  of  time  or  hours  of  work,  as  deter- 
mined by  local  agreement  or  law,  by  far  the  most  important 
consideration  is  the  quality  of  the  work  done,  and  this  in 
turn,  as  has  been  indicated,  is  largely  dependent  upon  wages 
paid.  High  wages  attract  good  workmen  and  by  competi- 
tion the  poorer  element  is  eliminated.  Difference  in  length 
of  a  working  day  and  of  wages  per  day  is,  however,  more 
apparent  than  real;  the  result  being  ultimately  about  the 
same,  the  conditions  naturally  equalizing  themselves  in 
quantity  and  quality  of  work  done.  Further,  a  day's  work 
may  be  based  upon  time  or  work  done,  and  as  in  practically 
all  other  kinds  of  work  the  latter  has  been  found  to  be 
much  more  satisfactory,  as  it  encourages  competitive  effort, 
which  means  both  more  work  done  and  a  higher  class  of 
work. 


244  ORE  MINING  METHODS 

In  development  work,  but  more  particularly  in  stoping,  it 
is  customary  to  pay  for  footage  drilled  or  volume  of  ore 
broken  down,  as  per  cubic  foot,  yard  or  fathom,  or  the  unit 
adopted  for  calculation  of  wages  earned  may  be  the  tonnage 
extracted,  which  is  in  reality  figured  on  the  basis  of  volume. 
The  unit  of  volume,  be  it  figured  in  feet,  yards  or  fathoms, 
or  tons,  is  that  commonly  chosen  for  contract  work. 

Supplies.  -  -  The  cost  of  supplies  varies  with  the  district 
and  is  dependent  largely  upon  transportation  facilities, 
quantity  consumed,  character  of  labor,  etc.  The  quality 
of  the  supplies  and  the  useful  amount  of  work  gotten  out 
of  them,  whether  fair  quality  or  poor,  is  also  comparable 
with  labor  and  is  dependent  more  or  less  directly  upon  the 
character  of  the  labor  employed. 

Power.  -  -  The  cost  of  power  in  any  particular  operation 
is  difficult  to  determine,  as  only  a  part  and  often  a  compara- 
tively small  part  is  consumed  in  the  particular  operation 
under  consideration.  In  the  case  of  stoping,  however,  the 
proportionate  amount  of  power  used  is  relatively  large 
compared  with  other  power  consuming  operations  under- 
ground, yet  while  the  error  in  estimation  of  amount  to  be 
charged  to  stoping  may  be  small,  it  exists  nevertheless, 
but  may  for  comparative  purposes  be  neglected  especially 
in  large-scale  operations  where  many  drills  are  employed 
and  the  output  is  consequently  large.  In  estimating  power 
costs  as  in  stoping  it  is  customary  to  distribute  or  'spread' 
the  cost  and  charge  an  equal  amount  to  each  machine  operat- 
ing, which  in  itself  may  be  a  source  of  error  in  that  the 
number  of  machines  in  actual  operation  from  day  to  day  as 


COST  OF  MINING 


245 


well  as  the  actual  time  of  operation  may,  together  with  their 
consumption  of  air,  vary  somewhat  causing  a  variation  in 
computed  costs  to  be  charged  to  a  given  machine  or  unit. 

Light.  —  The  cost  of  light  in  stoping  is  practically  a 
constant  quantity,  varying  but  slightly  in  the  various  dis- 
tricts, and  while  it  should  not  be  neglected  in  comparing 
costs  yet  the  difference  is  probably  more  apparent  than 
real.  With  light  as  with  labor  the  amount  of  work  done,  i .e., 
the  tonnage  produced  depends  largely  upon  the  character 
of  the  factor  involved.  While  illumination  is  an  important 
factor  in  mining,  yet  space  and  facilities  provided  determine 
the  number  of  men  that  can  be  employed  to  advantage. 

The  following  table  gives  the  comparative  cost  of  candles 
and  acetylene  lamps  in  a  number  of  mines:1 


Car- 

Num- 

bide 

ber  of 

N 
um- 

Con- 

Cost 

Cost 

Cost  of 

Men 

Car- 

per 

Candles 

Name  of  Company 

Em- 
ployed 

ber 
Using 

sump- 
tion per 

bide 
per  Lb., 

Lamp 
Shift, 

per 
Shift, 

Under- 

amps. 

Oz. 

Cents. 

Cents. 

Cents. 

ground. 

Shift. 

Homestake  Mining  Company  
Ray  Con.  Copper  Company  

1025 
1400 

1025 
I2OO 

8.0 
9-o 

3-50 
4.500 

1-75 
2.500 

7.00 

5.ooa 

Quincy  Mining  Company  

1389 

575 

6-7 

3-5°a 

i  .460 

Osceola  Con.  Mining  Company.  .  . 

625 

625 

6.0 

3-5° 

1.38 

United  Verde  Copper  Company.  .  . 

600 

575 

6-5 

5-5° 

2.23 

5-4° 

Bunker  Hill  &  Sullivan  Company. 

460 

208 

7.0 

5-25 

2.30 

6.18 

Calumet  &  Arizona  Mining  Com- 

pany. .  . 

IOOO 

60 

7    O 

5     TO 

2    4.O 

6.64 

Ohio  Copper  Mining  Company.  .  .  . 
Nevada  Con.  Copper  Company.  .  . 

96 

2OO 

37 

20 

/  •  ^ 

8.0 
4.0 

•  jw 
5-8o 
4.67 

*  .  ^f  '-' 

2.90 

I  .  12 

3-27 

Mammoth  Copper  Mining  Com- 

oanv 

I  2 

IO    O 

?  86 

3.66 

e     Is 

v)    •   OU 

O  •  XO 

a  Estimated. 

1  Acetylene  Lamps  for  Metal  Mines  by  Frederick  H.  Morley.     Mining 
and  Scientific  Press,  vol.  108,  p.  609. 


246  ORE  MINING  METHODS 

Support.  -  -  The  cost  of  supporting  mine  workings  is  far 
from  a  constant  quantity,  although  it  is  possible  that  there 
is  no  great  difference  where  the  same  methods  are  employed. 
Costs  of  support  range  from  a  few  cents  per  ton  to  more 
than  $i,  varying  with  character  of  ore  and  wall  rock,  and 
scale  of  operations. 

The  cost  per  ton  of  the  various  methods  of  support  is 
approximately  as  follows: 

Square-set  timbering 15  to  25  cents. 

Timber  with  top-slice about  1 7     ' 

Filling  with  filling  method 25  to  50 

Timber  with  caving  method 5  to  io 

Methods  of  handling  and  forming  timbers  as  in  the 
square-set  method  may  be  responsible  for  a  variation  of  as 
much  as  2  c.  to  5  c.  per  ton.  T.  S.  Carnahan  1  states  that 
the  Utah  Copper  Co.  mined  over  3,000,000  tons  of  ore  at  a 
cost  for  timber  of  less  than  5  c.,  which  could  hardly  have 
been  done  except  for  the  large  tonnage  produced. 

Handling.  —  Handling  of  ore  in  mines  usually  involves  a 
number  of  operations  such  as  clearing  stopes  and  loading 
cars  in  open  stopes  or  drawing  ore  from  closed  stopes  through 
chutes,  and  tramming  it  to  orepockets  or  the  shaft  station. 
The  transference  of  the  ore  to  the  surface  by  haulage 
through  a  tunnel  or  by  hoisting  may  be  a  continuation  of 
handling  or  an  entirely  different  operation  as  in  hoisting. 
There  is  a  wide  variation  in  the  -method  of  treating  the 
cost  of  handling  ore  and  consequently  considerable  con- 
fusion may  arise  in  comparing  similar  costs.  Reported 

1  Trans.  Am.  Inst.  Mining  Engrs.,  vol.  LIV,  p.  92.  Underground  Mining 
Methods  of  Utah  Copper  Co. 


COST  OF  MINING  247 

costs  of  handling  ore  varies  from  5  c.  per  ton  for  short  trips 
in  large  open  stopes  to  25  c.  for  hauls  of  several  thousand 
feet.  If  it  is  possible  to  give  an  average  it  might  be  placed 
at  about  15  c.  per  ton. 

GENERAL  MINING  COSTS 

Mining  expenses  as  given  under  this  head  comprise  all 
costs  connected  with  the  development  and  working  of  a 
mine,  and  are  similar  to  those  previously  outlined  except 
that  other  more  general  items  are  usually  considered,  such 
as  superintendence,  depreciation,  taxes,  amortization,  etc. 
The  value  of  such  data  is  therefore  of  a  general  nature 
and  is  useful  mainly  in  showing  expenditures. 

Mining  Costs.  -  -  T.  S.  Carnahan,  Trans.  Am.  Inst.  Mining 
Engrs.,  vol.  LIV,  p.  90.  Utah  Copper  Co. 

Per  Dry  Ton 

Labor $0.329 

Powder,  caps  and  fuse .  . o .  091 

Timber o .  049 

Motor  haulage o  .025 

Gravity  tramway o .  020 

Supervision  and  engineering o .  038 

Compressed  air o .  024 

Miscellaneous o .  1 1 1 

Total $o .  687 

William  Braden,  Bull.  Trans.  Am.  Inst.  Mining  Engrs., 
Oct.  1909,  p.  905.  Braden  Copper  Mines,  Chile. 

Per  Ton 

Ore-breaking $0.31 

General  mine-expense o .  06 

Development 0.12 

Underground  tramming o .  02 

Aerial  tramming 0.06 

Power o.oi 

Sampling  and  assaying o .  05 

General  expense 0.23 

Taxes,  insurance,  and  interest o .  04 

Total $0.92 


248  ORE  MINING  METHODS 

Hollinger  Mine,  Porcupine,  Canada.     Mining  &  Scien- 
tific Press,  vol.  106,  p.  661  (1913). 

Per  Ton 

General  and  superintendence $o .  1 79 

Diamond  drilling o .  027 

Sloping  and  driving i .  969 

Timbering  stopes o .  219 

Tramming o .  551 

Drainage  and  pipes 0.092 

Hoisting o .  1 70 

Dumping o .  063 

Drill  steel o.  298 

Assaying,  sampling,  and  surveying o .  064 

.Change  house  and  lights 0.013 

Handling  explosives 0.025 

Handling  waste o .  016 

Total $3.686 

Great    Boulder    Perseverance.     Eng.    &    Mining    Jour., 
vol.  93,  p.  1034  (1912). 

Per  Ton 

Wages  and  contracts $o .  900 

Explosives 0.156 

Drill  parts  and  air  lines o .  043 

Candles 0.018 

Air  for  drilling o .  105 

Not  specified o .  468 

Total $1.690 

West  End,  Tonopah.     Mining  &  Scientific  Press,  vol. 
107,  p.  272  (1913). 

Per  Ton 

Superintendent  and  foreman $0.135 

Breaking o .  802 

Timbering 0.090 

Tramming 0.372 

Hoist,  etc o. 200 

Ore  loading o.  233 

Ore  sorting o .  366 

Assaying,  sampling,  surveying .  . o .  091 

Surface,  ore  dump,  drayage o .  195 

Development o .  862 

General  expense o. 554 

Miscellaneous o .  262 

Total $4.162 


COST  OF  MINING  249 

Tonopah-Belmont.  Eng.  &  Mining  Jour.,  vol.  93,  p. 
936  (1912). 

Per  Ton 

Development $0.78 

Sloping 3 . 94 

Administration,  etc o. 719 

Total $5-439 

Many  other  general  mining  costs  are  available  from  com- 
pany reports,  but  it  is  hardly  necessary  to  add  to  those 
given  which  are  representative. 

DETAILS  OF  MINING  COSTS 

While  costs  of  the  special  operations  in  mining  are  not  as 
available  as  the  more  general  costs  yet  a  number  of  itemized 
statements  are  given  below  which  will  serve  to  show  the 
factors  involved  and  some  standard  costs. 

Development.  —  Montana-Tonopah  Mining  Co.  Mining 
&  Scientific  Press,  vol.  99,  p.  507  (1909). 

Per  Foot 

Drifting $6 . 56 

Cross-cuts 5-44 

Raises 4-65 

Winzes 11.92 

Total $28 . 57 

Portland  Gold  Mining  Co.  Cost  of  Mining,  Finlay.  The 
cost  of  drifting  is  itemized  as  follows: 

Per  Foot 

Tramming $i .  oo 

Pipe  and  trackmen 0.14 

Machine  men i .  88 

Machine  work,  air,  etc o .  97 

Repairs,  cars,  etc o .  08 

Explosives i  •  43 

Hoisting o.  46 

General  expense,  surveying,  etc 0.58 

Total .  .                                            $6 . 20 


250 


ORE  MINING  METHODS 


The  cost  of  other  development  work  carried  on  under 
similar  conditions  was  as  follows: 

Per  Foot 

Cross-cuts $6 .  23 

Winzes  and  raises 8 . 60 

Bunker  Hill  Sullivan,  Coeur  d'Alene.     Eng.  &   Mining 
Jour.,  vol.  95,  p.  1200  (1913). 

General  development  costs  are  as  follows: 

Per  Foot 

Foreman,  blacksmiths,  etc $0.312 

Miners 2 . 500 

Shovelers i .  650 

Explosives o .  990 

Timber  and  lagging o .  400 

Power,  labor  and  supplies ; o. 524 

Not  specified 0.774 

Total $7.150 

Cost  of  Raises  and  Winzes.     Elements  of  Mining,  Young, 

P-  432. _____ 

.  Location.  Raises.  Winzes. 

Per  Foot  Per  Foot 

Elkton,  Col $4.62  $12.51 

Portland,  Col 7.77  

Nevada  Hills,  Nev 6.30107.47  15. 27  to  19. 20 

Montana  Tonopah,  Nev 4 . 26  

Goldfield  Con.,  Nev ' 5.71  19 .47 

West  End,  Nev 6.68  13.39 

Standard  Con.,  Cal 3.66  5. 55  to  8. 75 

Mesabi,  Minn 3. 50  to  5.00  


The  cost  of  shaft  sinking  is  an  exceedingly  variable  quan- 
tity and  while  costs  could  be  given  covering  a  wide  range  of 
conditions  such  as  cross  section,  depth,  character  of  material 
worked,  amount  of  water  encountered,  method  employed, 
etc.,  yet  it  is  doubtful  whether  it  would  be  of  much  value  in 
this  connection. 

Stoping.  —  Costs  of  stoping  in  a  number  of  the  large  min- 
ing districts  of  the  United  States  are  given  in  this  connection 


COST  OF  MINING  251 

and  bring  out  some  interesting  facts  regarding  the  methods 
of  cost-keeping  and  the  items  which  go  to  make  up  the  costs. 

The  Copper  Mines  of  Keweenaw  Point,  Michigan 
The  following  data  were  collected  by  the  author  during 
a  period  of  some  four  weeks  spent  in  the  Wolverine  Mine 
in  1906.  There  are  three  methods  of  stoping  employed  in 
this  mine  and  generally  throughout  the  district,  which  are : 
drift,  raise  and  cutting-out  stoping.  Drift  stoping  is  the 
usual  method  of  working  from  a  level  and  consists  in  carry- 
ing a  face  25  ft.  high  practically  the  full  width  of  the  lode; 
the  lower  part  includes  the  drift  and  is  run  at  the  required 
grade  of  the  level.  When  possible,  the  lower  or  drift  portion 
is  attacked  first,  thus  forming  a  sump  or  opening  into  which 
the  remaining  upper  portion  may  be  broken.  The  average 
of  the  total  length  of  holes  drilled,  in  the  cases  observed, 
was  174  ft.,  while  the  time  of  drilling  averaged  from  obser- 
vations on  9  holes  in  each  case  was  as  follows: 

Average  depth  of  hole 5.6  ft. 

Mins.  Sees. 

Total  time  of  drilling,  per  hole ..     41     47 

Delays  in  drilling,  per  hole 19     29 

Actual  time  drilling  i  foot  of  hole 7     27 

The  total  time  of  drilling  174  ft.  of  hole  was,  therefore, 
21  hr.  and  45  min.,  or  two  shifts. 

Stoping  is  paid  for  by  the  fathom,  the  exact  amount 
varying  with  the  particular  stope;  the  price  runs  from  $5.50 
to  $9  and  averages  probably  $8  per  fathom.  A  fathom  is 
6  X  6  X  6  ft.  or  216  cu.  ft.,  8  cu.  yds.  The  average  height  of 
stope  is  12  ft.,  and  the  miners  are  paid  for  this  height  regard- 
less of  whether  the  actual  height  is  greater  or  less.  The 
height  of  the  drift  is  subtracted  from  the  height  of  the  stope 


252 


ORE  MINING  METHODS 


and  is  paid  for  as  drifting,  $5.50  being  the  usual  rate  per  ft. 
The  miner  then  receives  $8  per  fathom  for  19  ft.  width  of 
stope  12  ft.  high,  and  $5.50  per  foot  for  drift  6  ft.  wide  and 
12  ft.  high. 

The  1 74  ft.  of  holes  when  charged  and  fired  usually  break 
4/|  fathoms  or  36  cu.  yds  of  ore,  the  result  of  two  shifts' 
work.  The  delays  due  to  cleaning  up  and  other  causes  may 
reduce  the  output  somewhat,  but  it  is  seldom  less  than 
one-half  or  to  about  2\  fathoms  per  shift.  Working  two 
shifts  per  day,  as  is  the  practice,  58^  fathoms  are  broken 
down  per  month  of  26  working  days.  At  $8  per  fathom 
this  gives  $468  per  month  for  two  crews  of  two  men  each, 
and  from  it  all  expenses  have  to  be  deducted.  The  two 
crews  employ  a  drill  boy  between  them.  The  $4  charge 
for  drill  steel  is  also  divided  between  the  two  crews,  both 
crews  using  the  same  drill.  The  following  are  the  itemized 
expenses  of  one  crew  during  one  month  when  40  fathoms  or 
320  cu.  yds.  of  ore  were  taken  out: 


Total. 

Per 
Fathom. 

Per 
cu.  yd. 

7  boxes  powder  at 

$17.00                             .    . 

$IIQ    OO 

$2   071; 

$O    372 

2  boxes  candles  at 

$8  .  oo           

16.00 

0.40 

O    O? 

800  feet  fuse  at  i  < 

~ent  

8.00 

O.2O 

o  02  ? 

200  caps          .  .    . 

4.00 

o.  10 

0.0125 

3  gallons  oil  at  30 

cents 

o  oo 

o  02} 

o  oo^ 

Steel 

2    OO 

o  o^ 

o  0062 

D  ill  boy 

I  £  .  OO 

O    37< 

o  04.7 

Total 

Sl64.OO 

$4  .122 

$o.  ci? 

It  will  be  seen  that  350  pounds  of  powder  were  used  to 
remove  320  cu.  yds.  of  ore,  or  1.09  pounds  per  cu.  yd. 
Referring  to  the  above  cost  of  $4.122  per  fathom,  it  may 


COST  CF  MINING 


253 


be  noted  that  the  average  of  a  number  of  accounts  gave  an 
average  of  $4.24  per  fathom. 

In  raise  stoping  the  work  is  more  difficult  and  consequently 
the  cost  is  higher,  while  in  cutting-out  stoping  the  reverse 
is  true  and  the  cost  is  correspondingly  less.  The  price  paid 
per  fathom  is  the  same  as  with  other  stoping  operations. 
When,  however,  the  ground  breaks  readily  and  the  stopes 
are  large,  the  amount  paid  may  be  reduced,  even  as  low 
as  $5.50  per  fathom,  while  under  less  favorable  conditions 
a  higher  price  may  be  paid. 

The  usual  practice  in  the  district  is  to  pay  the  miner  on 
beginning  work  $60.00  per  month  for  the  first  two  months' 
work,  at  the  end  of  which  time  his  work  is  measured  up  and 
he  is  paid  $8  (or  the  amount  agreed  upon)  per  fathom  for 
stoping  and  $5.50  for  drifting  (in  drifting  and  drift  stoping). 
In  all  contracts  the  miners  furnish  supplies,  the  company 
providing  drills  and  steel. 

The  cost  of  stoping  in  a  number  of  mines  in  the  same  dis- 
trict and  for  the  years  1887  and  1892  are  shown  in  the 
following  tabulation : 


Mine. 

Year. 

Contract 
Price  per 
Fathom. 

1887 

$0.91 

Osceola 

1892 

1  1   09 

Atlantic 

1892 

•}   08 

Kearsarge    

1802 

Q.  <\7 

Tamarack  

1802 

ii  M 

Average 

$9  28 

The  ore  is  hard  and  does  not  drill  or  blast  very  easily. 


254  ORE  MINING  METHODS 

The  following  costs  have  been  compiled  from  reports  and 
data  regarding  the  respective  operations. 

The  Cripple  Creek  District,  Colorado 

The  distribution  of  costs  of  stoping  per  ton  in  the  Port- 
land gold  mine  as  given  for  the  year  1906  is  as  follows: 

Cost  per  Ton. 

Labor $i .  142 

Machines 0.270 

Tramming o .  029 

Explosives .  .  . ' .  o .  380 

Hoisting o .  230 

Supplies o .  036 

Superintendency,  assaying,  surveying,  etc 0.450 

Total :..  $Ti37 

The  labor  costs  may  be  analyzed  as  follows: 

Machine  men $o .  4761 

Trammers 0.3214 

Pipe  and  track  men 0.0357 

Timbermen o .  1666 

Timber  helpers 0.1428 

Total $1.1426 

The  ore  is  moderately  hard,  but  drills  and  blasts  readily. 

It  is  evident  on  examining  the  above  account  that  the 
work  is  thoroughly  systematized,  the  idea  being  to  dis- 
tribute to  each  and  every  operation  involved  its  propor- 
tionate amount  of  expense.  There  is  also  indication  of  a 
1  spread'  of  costs,  especially  in  the  items  of  machine  drills, 
tramming,  hoisting,  superintendency,  etc.  It  is  obvious 
that  with  such  a  system  a  very  effective  check  upon  the 
various  operations  is  possible. 


COST  OF  MINING  255 


The  Alaska-Treadwell  Mines,  Douglas 
Island,  Alaska 

The  successful  operation  of  the  large  gold  mines  of 
Douglas  Island,  Alaska,  is  made  possible  by  a  number  of 
conditions,  among  which  none  is  of  more  importance  than 
that  of  organization. 

The  large  scale  of  the  operations  and  the  comparative 
low  grade  of  the  ore  practically  necessitate  very  careful  and 
systematic  management  in  order  that  the  work  may  be 
profitably  carried  on.  The  figures  given  below  are  for  the 
years  1901  and  1902. 

Cost  per  Ton 

Machine  work $0.3793, 

Rock  breaking 0.3124 

Tramming o .  0359 

Hoisting o .  0486 

Explosives o .  2269 

Light o .  0085 

Total $1.0116 

Ore  is  hard  and  firm,  but  drills  and  blasts  quite  easily. 

Here,  as  in  the  last  mentioned  case,  an  attempt  has  been 
made  to  distribute  costs,  charging  to  each  operation  the 
proportionate  amount  of  expenditure,  but  unless  the  dis- 
tribution of  costs  is  carefully  made  considerable  confusion 
and  inaccuracy  may  result. 


256 


ORE  MINING  METHODS 


The  Lead- Silver  District,  Cceur  d'Alene,  Idaho 

The  detailed  cost  of  stoping  in  the  Bunker  Hill  and  Sulli- 
van Mine  for  the  year  1908  is  as  follows: 


Details  for  Labor  and 
Supplies. 

Total  for 
the  Year. 

Average 
per  Ton  for 
the  Year. 

Highest  Cost 
per  Ton  for 
I   Month 
During  the 
Year. 

Lowest   Cost 
per  Ton  for 
i  Month 
During  the 
Year. 

Foremen,  bosses,  black- 
smiths,       machinists, 
tool-packers,  etc 

$60,082    27 

$o   185 

$o   191 

$o   165 

Timberman     and     car- 
penters   

2C.IOQ    38 

o  .  076 

o  .  082 

0.063 

Miners 

125   148    48 

O    37Q 

O    4OO 

O    33Q 

Car-men 

i  5  9  1  8  oo 

o  048 

o  042 

o  058 

Shovelers 

I  3  3    I  76     CO 

O    4C3 

o  4^0 

O    370 

Power  labor  .    ... 

7,708  40 

O    O2  3 

o  027 

O.O2I 

Repair  labor  
Explosives  

7,492.70 

30,010.  37 

O.O23 
0.091 

0.025 

O.  Ill 

0.021 

0.087 

Illuminants  

7,482.08 

O.  O23 

0.026 

O.OI7 

Lubricants  

1,329.87 

O.OO4 

o  .  004 

0.006 

Iron  and  steel  
Miscellaneous  supplies.  . 
Timber  and  lagging  .... 
Power  supplies  
Wood 

4,158.20 
11,667.61 
61,629.00 

7,876.30 

9  292  80 

0.013 

°-°35 
0.186 
0.024 
o  028 

0.014 

0.032 
0.199 

0.024 

O    O3O 

0.012 
0.025 

o.  165 

0.027 

o  030 

Stable  and  stock  

2,297.20 

0.007 

0.007 

<_>.UJW 

0.006 

Total 

$511,288.16 

$1.548 

$1  .  664 

$1  .421 

Nov. 

May. 

Ore  is  not  particularly  hard  to  drill  and  blast. 

The  comparatively  high  cost  of  timber  as  shown  in  the 
above  table  is  due  to  the  fact  that  square-set  timbering  is 
an  important  adjunct  to  the  mining  of  the  ore  in  this  district. 
The  high  cost  of  labor,  particularly  for  shovelers,  is  due  to 
the  necessity  of  freeing  the  stopes  from  ore  and  placing 
waste-filling. 


COST  OF  MINING  257 

The  Goldfield  Consolidated  Mines  Company, 

Goldfield,  Nevada 

The  costs  of  stoping  during  ten  months  of  1909  are  given 
in  the  following  tabulation: 

Cose  per  Ton 

Labor $i .  24 

Supplies o .  66 

Power o .  03 

Department 0.25 

Construction 0.02 

General 0.02 

Total $2.38 

Ore  is  a  fair  average  for  drilling  and  blasting. 

The  first  three  items  given  are  regular  and  legitimate 
cost  for  this  kind  of  work;  the  last  three  are  indeterminate, 
and  while  they  may  be  composed  wholly  or  in  part  of  ex- 
penditures necessary  for  the  proper  carrying  on  of  the  work 
of  stoping,  yet  their  designation  leaves  this  in  doubt. 

The  Joplin  Lead-Zinc  District,  Missouri 
The  cost  of  breaking  ground  in  the  Joplin  district  varies 
considerably  owing  to  character  of  ground,  which  ranges 
from  very  hard  to  very  soft.     The  usual  conditions  existing 
in  the  sheet  ground  in  the  vicinity  of  Joplin,  Webb  City, 
etc.,  permit  the  ore  to  be  broken  down  at  moderate  cost. 
The  following  costs  are  representative  of  the  district: 

COST   OF   STOPING   IN    1901 

2  machine  men  at  $3.00 $6 . oo 

2  machine  helpers  at  $2.50 5.00 

2  shovelers  at  $2.50 5 . oo 

i  blacksmith  at  $2. 50 2 . 50 

i  ground  boss  at  $3.00 3  •  oo 

Explosives 6 .  oo 

Incidentals 3 .  oo 

Total $30 . 50 


258  ORE  MINING  METHODS 

Drilling  and  blasting  are  fairly  easy,  although  variable, 
owing  to  character  of  ground  encountered. 

The  $30.50  represents  the  expenditure  for  one  day  when  75 
tons  of  ore  are  broken;  the  cost  per  ton  was  then  about  $0.40. 

Other  more  detailed  costs  of  operations  that  go  to  make 
up  the  cost  of  breaking  ground,  also  related  cost  data  ex- 
pressed in  cents  per  ton,  are  as  follows: 

COST  OF   STOPING   IN   1903 

Cost  of  drilling,  hand  work $o .  06800 

Cost  of  drilling,  machine  work 0.05600 

Cost  of  drill  steel 0.00878 

Cost  of  powder,  caps  and  fuse o .  04050 

Cost  of  oil  for  lamps o .  00080 

Cost  of  timbering,  soft  ground o .  00045 

Cost  of  pumping,  mine  pumps o .  00005 

Cost  of  track o .  00009 

Cost  of  shoveling o .  03900 

Cost  of  labor  underground o .  19890 

Cost  of  hoisting o .  02860 

Cost  of  tramming o .  02600 

Cost  of  air  compressor 0.00150 

Total $0.46867 

The  cause  of  the  variation  of  7  c.  per  ton  noted  above  is 
difficult  to  explain,  but  is  slight  when  the  factors  influ- 
encing the  costs  are  considered.  The  period  during  which 
the  figures  from  which  the  averages  were  calculated  is  a 
controlling  factor  if  short,  otherwise  not. 

The  War  Eagle  Mine,  British  Columbia 

The  costs  previously  given  are  for  mines  located  in  the 
United  States.  The  cost  of  stoping  as  given  in  the  com- 
pany's report  of  the  War  Eagle  Mine  for  the  year  1909 
illustrates,  even  to  better  advantage  than  in  the  previous 


COST  OF  MINING 


259 


cases  cited,  the  spread  of  costs,  involving  practically  all 
operations  having  to  do  with  the  underground  work.  The 
following  costs  are  figured  on  a  ton  basis. 

1.  Drilling $i .  53 

2.  Tramming  and  shovelling o. 53 

3.  Timbering o.  29 

4.  Hoisting o.  13 

5.  Smithing 0.15 

6.  Ore  sorting o .  01 

7.  General  labor o .  30 

8.  Air •. 0.21 

9.  Candles  and  illuminating  oil o .  03 

10.  Explosives 0.02 

11.  Drills  and  fittings 0.25 

12.  Mine  supplies o .  05 

13.  Lumber  expense 0.04 

14.  Stable  and  teaming o .  03 

15.  Assaying o .  04 

16.  Surveying o .  05 

17.  Electric  lighting , 0.02 

18.  Salaries o .  03 

19.  Office  expenses 0.18 

20.  General  expenses o .  05 

Total $3-95 

Ore  drills  and  blasts  moderately  well. 

In  comparing  this  cost  of  stoping  with  others  which  have 
not  been  so  extensively  distributed  it  would  be  necessary 
to  eliminate  a  number  of  items,  those  chosen  for  actual  use 
being  i,  5,  8,  9,  10,  n  and  12.  The  items  2,  3,  and  6  might 
very  properly  in  this  case  be  included,  especially  3,  as  square- 
set  timbering  is  employed.  The  item  of  drilling  is  probably 
labor  of  operating  drills,  while  the  air  item  indicates  the 
cost  of  power.  Drills,  fitting  and  mine  supplies  consist 
of  steel  and  other  drill  repairs. 

Stoping  at  the  Tonopah-Belmbnt  Mine.  Eng.  &  Mining 
Jour.,  vol.  93,  p.  936  (1912). 


260  ORE  MINING  METHODS 

Per  Ton,  Cents. 

Miners 44 . 500 

Shovellers 33 . 900 

Trammers 19 . 200 

Timbermen  and  helpers 97 . 800 

Filling 4 .  200 

Piston-drill  repairs 5 .  ooo 

Stoping-drill  repairs 2 . 900 

Steel  and  sharpening 7 . 100 

Explosives 28 . 600 

Hoisting  to  surface 30 . 900 

Auxiliary  hoisting . 9 . 400 

Ore  sorting  and  loading 27.300 

Total 310 . 800 

Stoping  at  the  Bunker  Hill,  Sullivan  Mine.  Mining  & 
Scientific  Press,  vol.  106,  p.  727  (1912). 

Per  Ton. 

Timbermen  and  carpenters $o .  086 

Foremen,  bosses,  etc °  • !  77 

Miners 0.367 

Carmen 0.052 

Shovellers o .  366 

Power  labor 0.027 

Repair  labor o .  026 

Explosives o .  075 

Illuminants o .  020 

Lubricants o .  003 

Iron  and  steel 0.012 

Miscellaneous  supplies o .  035 

Timber  and  lagging 0-215 

Power  supplies o .  045 

Wood 0.034 

Total $i  .540 

An  examination  of  the  above  data  brings  out  the  fact 
that  the  larger  the  company,  and  consequently  the  operation, 
the  more  detailed  are  the  working  costs,  which  is  not  shown 
to  particularly  good  advantage  either  owing  to  the  com- 
bining of  certain  costs  in  this  connection.  By  increasing 
the  number  of  items  in  an  operation  and  putting  the  collec- 
tion of  the  data  upon  which  the  costs  are  based  in  the  hands 


COST  OF  MINING  261 

of  a  sufficient  number  of  competent  men  it  is  possible  to 
secure  fairly  accurate  results,  but  there  is  always  danger  of 
lax  work  being  done,  short  cuts  being  taken  and  approxi- 
mations made,  which  if  persisted  in  mean  inaccurate  and 
untrustworthy  returns.  Another  cause  of  error,  aside  from 
poor  organization  of  the  data-collecting  force  and  arising 
from  the  distribution  of  costs,  is  that  often  no  account  is 
taken  of  variations  in  work  done  by  the  factors  involved. 
This  can  be  illustrated  by  the  one  item  of  power,  the  cost 
of  which  is  commonly  distributed  uniformly  over  all  the 
machines  of  a  kind,  as  machine  drills  in  stoping.  It  is  rarely 
the  case  that  out  of  100  or  even  50  drills  employed  in  stoping, 
all  are  being  operated  at  the  same  time,  i.e.,  continuously 
day  after  day.  An  ordinary  piston  drill  is  seldom  running 
more  than  one-half  the  time  that  it  is  supposed  to  be  in 
operation.  The  advent  of  the  air-hammer  drill,  which  is 
now  being  largely  employed  in  stoping  operations,  might 
be  supposed  to  change  these  conditions,  for  where  used  in 
similar  work  as  the  piston  drill  it  is  running  the  greater  part 
of  the  time.  It  would  seem  then  that  the  consumption 
of  air  should  be  greater,  but  experience  shows  that  the  air- 
hammer  drills  use  considerably  less  air,  approximately  one- 
half  that  of  a  piston  drill.  Where  continuous  operation  is 
maintained  under  conditions  such  as  permit  the  drilling  of 
a  greater  footage  than  with  piston  drills,  there  would  have 
to  be  a  different  unit  of  cost  calculated  if  the  two  types  of 
drills  were  operating  in  the  same  mine,  which  would  lead 
to  still  further  complication  in  the  estimation  of  costs  of 
power.  Further,  the  power  required  for  each  drill  varies 


262 


ORE  MINING  METHODS 


considerably  both  with  its  period  of  service  and  the  skill 
and  experience  of  its  operators,  and  to  a  less  extent  with 
its  distance  from  the  source  of  power,  as  in  the  use  of  air 
drills.  In  order,  then,  to  show  the  correct  cost  of  power  for 
a  drill  employed  in  stoping  it  is  necessary  to  know  at  least 
the  number  of  drills  that  are  in  actual  operation,  which  can 
only  be  determined  by  daily  inspection.  This  requires  a 
constant  and  often  daily  change  of  unit  costs,  which  is 
somewhat  confusing.  A  fair  and  uniform  charge  per  drill- 
shift  is  probably  preferable,  which  unit  cost  multiplied  by  the 
number  of  units  will  at  once  give  the  power  cost  desired. 

The  cost  per  drill-shift  for  various  styles  of  compressors 
and  at  different  altitudes  is  given  in  the  following  table. 


Cost  per  1000  cu. 
ft.  Free  Air,  Com- 

Cost per  Drill- 

_u  :f4- 

pressed. 

Snitt* 

Maximum 

Total 

| 

Style  of 
Compressor. 

Capacity, 
cu.  ft.  Free 
Air  per 

Cost 
per 
H.P. 

Sea 
Level. 

5000 
ft. 
alt. 

10,000 

ft. 

alt. 

Sea 
Level. 

sooo 
ft. 

alt. 

10,000 

ft. 
alt 

Minute. 

Hour. 

cents  . 

cents. 

cents. 

cents. 

dols. 

dols. 

dols. 

Simple  steam 

(non-condensing) 

2OO 

2.  2 

5-9 

5-3 

4-8 

2.07 

2  .  22 

2.40 

Compound  steam 

(non-condensing) 

300 

i-5 

4.0 

3-6 

3-3 

1.40 

1.50 

1-65 

Simple  steam 

(condensing)  .... 

2500 

I  .0 

2.7 

2.4 

2.2 

•95 

I  .01 

I.  10 

Compound  steam 

(condensing)  .... 

3000 

0.8 

2.2 

1.9 

1.8 

.76 

.8l 

.88 

The  cost  will  vary,  of  course,  with  the  character  of  rock 
or  ore  drilled.  The  above  figures  were  calculated  from  data 
collected  from  work  done  in  granite.  The  compressors  are 
all  two-stage,  intercooled. 

The  value  of  cost  data  is  twofold,  namely,  it  may  be 
relative  and  comparative;  the  former  is  useful  as  showing 


COST  OF  MINING  263 

the  relative  expenditures  for  various  kinds  of  work  in  the 
same  mine,  the  latter  may  serve  a  useful  purpose  in  the 
determination  of  the  cost  of  the  proposed  operations  in  the 
same  or  in  other  districts.  The  former  may  be  accurate, 
the  latter  may  be  very  inaccurate  and  unreliable  owing  to 
the  necessity  of  dealing  with  many  conditions  which  are 
largely  unknown  and  conjectural  at  best. 

The  question  as  to  how  cheaply  the  various  operations  in 
mining  can  be  done,  or  whether  they  can  be  done  as  cheaply 
in  one  district  as  in  another  or  in  different  mines  of  the  same 
district,  will  have  to  be  determined  by  ascertaining  the  cost 
of  the  separate  items  making  up  the  total  costs  in  the  work 
to  be  compared.  This  may  be  accomplished  in  a  number  of 
ways;  which  is  chosen,  will  depend  largely  upon  the  accuracy 
of  the  results  desired.  In  order  that  cost  data  may  be  useful 
they  must  indicate  an  amount  or  expenditure  composed  of 
a  number  of  regular  factors  common  to  similar  operations 
and  independent  of  locality.  These  factors  to  be  of  the  most 
value  should,  for  comparative  purposes,  be  figured  on  a 
percentage  basis. 

The  differentiation  between  cost  of  various  operations, 
rendering  each  account  simple  and  complete  in  itself,  would 
seem  desirable.  Tramming,  hoisting,  etc.,  might  readily  be 
placed  under  a  class  of  operations  separate  from  stoping, 
as  handling  ore  outside  the  stope.  In  other  words,  charge 
to  stoping  just  those  operations  that  are  confined  to  the 
stopes,  thus  localizing  the  operations  and  their  costs.  Sim- 
plicity, both  with  regard  to  the  management  of  the  work 
and  the  collection  of  data  upon  which  costs  are  figured,  is 


264 


ORE  MINING  METHODS 


of  probably  the  most  importance,  and  this  can  be  effected 
to  good  advantage  by  contract  work,  where  the  miner  keeps 
his  own  accounts  largely,  or  at  least  is  sufficiently  inter- 
ested to  keep  close  check  upon  them.  The  operator,  in 
turn,  checks  off  results  as  the  output  resulting  from  the 
miners'  labor,  and  pays  for  work  actually  done.  The 
contract  work  previously  mentioned  as  in  the  case  of  the 
Wolverine  Mine  illustrates  the  point. 

The  two  general  contract  systems  employed  are :  measure- 
ment of  volume,  as  '  advance '  in  drifting  and  volume  of  ore 
broken  in  stoping,  and  the  hole-contract,  i.e.,  the  measure- 
ment of  the  number  of  feet  of  hole  drilled.  The  following 
data  show  the  saving  effected  by  the  employment  of  the 
contract  system  in  place  of  the  wage  system  in  stoping  as 
was  done  in  the  Center  Star  and  War  Eagle  mines  of  Ross- 
land,  British  Columbia: 


Contract 
(hole)  System, 
per  Ton. 

Wage  System, 
per  Ton. 

$0.^6 

)     * 

Blasting 

O    O2I 

\    $0.750 

Explosives     ...                         ..        

O    IOO 

O    II? 

Total  .                  

$O.477 

$0.865 

The  advantage  gained  by  the  company  was  also  a  gain 
for  the  miner  in  that  his  daily  wage  was  increased  from 
$4  to  $4.25,  as  against  $3.50  under  the  wage  system.  The 
increased  wage  shows  both  a  saving  per  ton  in  cost  of  stop- 
ing and  an  increased  tonnage  of  ore  broken,  a  natural  result 
due  to  better  pay,  as  previously  indicated. 


COST  OF  MINING 


265 


It  might  be  stated  in  this  connection  that  the  contract 
system,  in  which  the  miner  is  paid  by  the  fathom  or  other 
unit  of  volume,  has  proven  unsatisfactory  in  these  mines 
owing  to  the  difficulty  of  measuring  exactly  the  volume  of 
ore  broken  in  the  very  irregular  stopes  —  the  pay-shoots 
being  very  irregular  in  outline. 

Support.  —  In  certain  kinds  of  work,  as  working  slightly 
dipping  deposits,  square-set  mining,  etc.,  the  cost  of  support 
may  be  a  necessary  and  important  part  of  the  cost  of  break- 
ing ore  or  stoping,  being  usually  figured  on  the  tonnage 
basis.  A  single  case  will  suffice  to  show  the  cost  per  ton 
under  average  conditions,  and  for  comparative  purposes  the 
cost  under  two  different  systems  of  working  are  given.  The 
figures  given  below,  prepared  by  Mr.  B.C.  Yates,  are  for  the 

AMOUNT  AND  COST  OF  TIMBER,  SQUARE-SET  METHOD 


Name  of  Piece. 

Number 
of 
Pieces. 

Lineal  Feet 
or  Feet 
Board 

Measure. 

Cost  of 
Material. 

Labor, 
Sawing 
and 
Framing. 

Total. 

Sill-floor  posts  
Upper-  floor  posts.  .  . 
Caps 

421 
2,077 
2,410 

3>65° 
16,616 

17,2^ 

$474.50 
2,160.08 

1,72'?.  I"? 

$96.83 

477-71 
t;o6.  10 

$571-33 
2>637-79 

2.22O.  2< 

Ties                    .      .  . 

2,261 

12,4^5 

1,616.  55 

474.81 

2.O9I  .  36 

Sills,  203  long,  382 

4,1:77 

226.85 

22.69 

249.54 

Lagging  . 

13,020 

75,906 

3,795.  30 

379.53 

4,174.83 

Lagging  strips  
Wedges 

2,410 

2,  3^2 

4,025 
784 

64.82 

I^.  T.T. 

30.00 
ii  .  76 

94.82 
2Z.OQ 

47  sill-floor  chutes, 

311.68 

16.25 

327.91 

215  upper-floor  bins, 
complete  

786.22 

37.90 

824.  12 

Ladders  

14 

117 

1.99 

3.50 

5-49 

Labor  placing  tim- 

4,745.00 

Breakage  (10%)  of 
lagging,  5%  posts, 

7Q3.Q7 

Totals 

$11,174.47 

$2.057.08 

$•18,770.52 

266 


ORE  MINING  METHODS 


old  square-set  method  and  a  more  recent  method  now  being 
largely  employed  in  the  Homestake  mines  of  South  Dakota. 

AMOUNT  AND   COST   OF  TIMBER,  HOMESTAKE   METHOD 


Name  of  Piece. 

Number 
of 
Pieces. 

Lineal 
Feet  or 
Feet  Board 
Measure  . 

Cost  of 
Material. 

Labor, 
Sawing 
and 
Framing. 

Total. 

Sill-floor  posts  
Cans 

421 
410 

3>65° 

2,2=;o 

$474.50 

2Q7  .  1C 

$96.83 
86.10 

%7i-33 

370   2< 

Ties  

381 

2,O<K 

272  .  1< 

80.01 

1Z2  .  T.6 

Sills,  long  
Sills,  short  
Lagging.  . 

203 
382 

I,7C2 

2,436 

2,101 

IO,2I4 

121.  80 
105.05 

Sio.  70 

12.  18 
10.50 
<i  .07 

I33-98 
115-55. 
(:6l.77 

Lagging  to    protect 
track               .    . 

764 

4  4^4 

222     7O 

22    27 

244   07 

Relief  lagging  

1,684 

I  7,472 

673    OO 

67     36 

74O.  06 

Wedges  

200 

66 

I  .  12 

I  .00 

2.12 

Totals 

$2,674.97 

$427.32 

$3,102.29 

AMOUNT  AND   COST   OF  TIMBER   IN  MAN-WAYS,  HOME- 
STAKE  METHOD 


Lineal 

Labor, 

Name  of  Piece. 

Number 
of 

Feet  or 
Feet  Board 

Cost  of 
Material. 

Sawing 
and 

Total. 

Pieces. 

Measure. 

Framing 

Upper-floor  posts.  .  . 

96 

768 

$99.84 

$22.08 

$121  .92 

Caps.  .  , 

48 

264 

7  J.     7  *> 

10.08 

44.40 

Ties 

48 

264 

34-  ^2 

1  0  .  08 

44.40 

Lagging,  floors  

96 

560 

28.00 

2.80 

30.80 

LaGTffing   sides 

72O 

4,197 

209.85 

20.98 

230.83 

I     44-O 

4^7   1  DS 

22    8< 

22.8? 

Ladders  

28 

2T.< 

4.00 

7.00 

11.00 

Labor  standing  sill- 

floor  timbers  .... 

758.16 

Totals 

$1,108.15 

$500.  34 

$4,366.65 

The  costs  of  the  two  methods  were  $0.257  and  $0.060 
per  ton  figured  on  an  output  of  73,000  tons  from  the  stope, 
thus  showing  a  saving  of  $0.197  Per  ton  in  favor  of  the 
Homestake  method. 

Comparative  costs  of  a  stope  in  a  Cripple  Creek  gold 


COST  OF  MINING  267 

mine  where  stulls  and  filling  were  used  are  given  in  the 
following  table. 

STULLED    STOPE 

143  stulls  at  $2.50 $357-50 

Lagging 10 .  oo 

Total ., $367 . 50 

FILLED   STOPE 

Interest  on  $4640  for  4.5  months  at  6  per  cent $104.40 

Timber  (one-third  of  $357.50) 119.17 

Total $223.57 

Saving  in  favor  of  the  filled  stope  $143.93.  The  filled 
stope  had  in  this  case  a  filling  of  ore  valued  at  $20  per  ton, 
which  is  considered  as  so  much  capital  tied  up  for  the  time 
being.  As  G.  E.  Wolcott,  who  furnishes  these  data,  points 
out,  there  is  comparatively  small  difference  between  the 
two  cases  when  considered  from  the  standpoint  of  amount  of 
ore  broken.  Further,  there  is  a  greater  difference  with 
low-grade  and  a  less  with  higher  ore,  which  with  the  high- 
grade  ore  may  even  reach  a  point  where  the  method  of 
support  by  stulls  may  be  cheaper  than  with  filling.  Aside 
from  the  consideration,  of  costs  there  is  a  decided  advantage 
in  favor  of  ore-filled  stopes  or  the  so-called  ' reserves'  of 
ore,  where  the  conditions  are  suitable  for  such  a  method  of 
working.  Aside  from  facilitating  work  at  the  face,  in  con- 
venience of  placing  and  setting  up  drills  and  giving  the 
miner  ready  access  to  the  working  face,  its  great  advantage 
lies  in  the  regulation  of  output  of  the  mine. 

COST  OF  OPEN  CUT  MINING 

A  few  costs  are  given  for  open  cut  mining  which  method 
has  now  become  of  the  first  importance  in  the  production  of 
low-grade  ores  such  as  iron  and  copper. 


268  ORE  MINING  METHODS 

Open  Cut  Mining  at  the  Boston  Con.  Mine,  Utah.  Mining 
&  Scientific  Press,  vol.  99,  p.  474. 

Per  Ton. 

Supervision $o .  0034 

Operation,  well  drills 0.0134 

Operation,  air  drills o .  0066 

Blasting o .  0308 

Operation,  steam  shovels o .  0588 

Operation,  railroads 0.0435 

Dumps o .  0147 

Operation,  tram  and  ore  bins 0.0020 

Shop,  tools  and  machinery o .  0078 

Maintenance  of  buildings o .  0002 

Miscellaneous o .  0013 

Total $0.1825 

Costs  of  Open  Cut  Work  in  the  Mesabi  Iron  Range.  J.  S. 
Lutes.  Trans.  Lake  Superior  Mining  Inst.,  vol.  18,  p.  134. 

Stripping  ordinary  glacial  drift,  30  cents  a  cu.  yd. 
Stripping  ordinary  paint-rock,  30  cents  a  cu.  yd. 
Stripping  ordinary  broken  taconite,  75  cents  a  cu.  yd. 
Stripping  ordinary  solid  taconite,  $1.00  a  cu.  yd. 
Steam-shovel  mining,  ordinary  ground,  1 5  cents  a  ton. 

The  last  item  compared  with  underground  work  shows  a 
difference  of  60  cents  per  ton  in  favor  of  steam-shovel  work. 

The  economical  limit  of  stripping  is  about  as  follows: 

One  yard  of  overburden  may  be  removed  for  i  ton  of  ore 
mined. 

For  each  foot  in  depth  of  ore  removed  2  feet  of  overburden 
may  be  stripped. 

A  depth  of  150  ft.  is  the  maximum  depth  that  can  be 
stripped. 


INDEX 


Adit  or  adit-level,  39. 

Air  hammer  drill  in  stoping,  261. 

Alaska-Treadwell  mines,  142,  255. 

cost  at,  255. 

depth  of  open  cuts,  208. 
Angle  of  repose,  79. 
Angle  of  underlie,  9. 
Arch  pillars,  7,  164. 

in  Combination  Mine,  106. 

in  Homestake  Mine,  169,  171. 

in  Trimountain  Mine,  130. 
Arching  of  roof,  21. 

dome  of  equilibrium,  21. 

in  Homestake  Mines,  174. 
Atlantic  Mine,  128. 
Alaska-Treadwell  Mines: 

stopes  in,  21. 

Back  of  stopes,  147. 

in  Alaska-Treadwell  mines,  147. 
Back-filling  method,  advantage  and  dis- 
advantage   of,    in    St.    Lawrence 
Mine,  122,  125. 

Homestead  Mine,  167,  169. 
Back-stoping,    in    Combination    Mine, 
1 06. 

in  Hecla  Mine,  108. 
Baltic  Mine,  128. 
Battery  of  stulls.  n. 
Bedded  deposits,  stoping  in,  97. 
Benches  in  stopes,  62. 

height  of,  62. 

Bessemer  and  non-Bessemer  ore,  80. 
Birmingham  iron  mines,  Ala.,  97. 
Blasts,  mammoth,  212. 
Blind  drifts  in  Alaska-Treadwell  mines, 

145- 

Blocking  in  Hecla  Mine,  no. 
Breaking  ore: 

bull-dozing,  147,  193. 

cost  of,  250. 

in  iron  mines,  Ala.,  97. 

in  Lake  Superior  iron  mines,  251. 

in  milling  method,  227. 

in  open  cut  work,  hand  mining,  268. 

method  of  contracting  for,  264. 
Breaking- through  in  stoping,  130,  147. 


Breast  stoping: 

advantage  of,  64,  70. 

application,  64,  70,  98. 

disadvantage  of,  65,  70. 
Broken  Hill  mines,  Australia,  156. 
Bulkheads: 

advantages  of,  13,  23. 

disadvantages  of,  23. 

used  with  filling,  3. 

Bull-dozing  in  Alaska-Treadwell  mines, 
147. 

in  glory-hole  mining,  229. 
Bunker  Hill-Sullivan  mines,  114. 

Cantilever  support  for  back  of  stope, 

161. 
Caving: 

advantages  of,  25. 

application  of,  5. 

disadvantages  of,  25. 

in  diamond  mines,  199. 

in  Lake  Superior  iron  mines,  176,  177, 
231. 

in  Mercur  mines,  Utah,  135,  137. 

in  Miami  Mine,  194. 

in  Susquehanna  Mine,  186. 

methods,  5,  21. 

references  to,  205. 

when  applicable,  5,  21. 
Central  Mine,  Mo.,  240. 
Chambers  in  diamond  mines  of  South 

Africa,  195. 

Chinaman  ore  chute,  89. 
Chutes: 

block-holes,  84. 

branched,  44,  117. 

broken-slope,  44,  88. 

chinaman,  89. 

cribbed,  85,  87,  121. 

distance  apart,  84,  117,  123. 

for  loading  cars,  88,  101. 

in  Broken  Hill  mines,  161. 

in  Bunker  Hill-Sullivan  mines,  115. 

in  Cceur  d'Alene  mines,  88. 

in  Gold  Prince  Mine,  140. 

in  Hecla  Mine,  in. 

in  Homestake  mines,  169,  172. 


269 


270 


INDEX 


Chutes: 

in  Lake  Superior  mines,  178,  183. 

in  milling  method,  225. 

in  St.  Lawrence  Mine,  123. 

in  Tonopah  Mine,  101. 

mill  holes,  130,  229. 

in  Trimountain  Mine,  130. 

sheet  metal,  4,  79,  80. 

stope-chutes,  85. 

stoppage  of.  88. 

timber,  85. 

Cceur  d'Alene  mines,  Idaho,  88,  256. 
Combination    Mine,    Goldfield,    Nev., 
104. 

milling  method,  106. 
Combined  stoping: 

advantages  of,  63,  64. 

disadvantages  of,  65. 

limits  of,  63. 
Comstock  Lode: 

square-sets  and  filling,  4. 

temperatures  of,  240. 

timbering  in  mines,  3. 
Contract  systems,  264. 
Conveyors  in  stopes,  80. 

the  monorail,  80. 

Corrals  of  waste  in  Hecla  Mine,  113. 
Cornish  system  of  stoping,  58. 
Corduroy  in    Comstock  Lode,  3. 
Costs: 

contract  stoping,  264. 

detailed,  241,  249. 

drill-shift,  262. 

factors  influencing,  242. 

general,  247. 

in  Alaska-Tread  well  mines,  255. 

in  Bunker  Hill-Sullivan  Mine,  260. 

in  Coeur  d'Alene  mines,  256. 

in  Copper  mines  of  Michigan,   194, 

in  Cripple  Creek  mines,  254. 

in  Goldfield  Mine,  Nevada,  257. 

in  Joplin  district,  Missouri,  257. 

in  War  Eagle  Mine,  B.  C.,  258. 

method  of  computing,  244. 

of  breaking  ore,  239. 

of  development,  249. 

of  labor,  effect  on  stoping,  240,  241, 

243- 

of  light,  245. 
of  open  cut  mining,  267. 
of  power,  240,  244,  261. 
of  stoping,  250,  251,  252,  253,  256, 

257,  259,  260. 
of  supplies,  240,  244,  265., 
of  support,  238,  246. 
of  timber,  246. 
value  of  data,  247,  262. 


Covers  in  open  cut  mining,  215. 

thickness  of,  215. 
Cribs: 

advantages  of,  23. 

application  of,  13. 

crib-work  in  Broken  Hill  mines,  161. 

disadvantages  of,  23. 

in  stopes,  13. 

used  with  filling,  13,  23. 
Cripple  Creek: 

cost  of  stoping,  254. 
Cross-cuts: 

cost  of,  25. 

in  Alaska-Treadwell  mines,  144. 

in  Broken  Hill  mines,  158,  159,  162. 

in  development,  42. 

in  diamond  mines,  195.  196. 

in  Gold  Prince  Mine,  140. 

in  Homestake  mines,  167,  172. 

in  Lake  Superior  mines.  177,  181,  185. 

in  Miami  Mine,  190,  191. 

in  mines,  136. 

in  St.  Lawrence  mines,  123. 
Cutting-out  stoping: 

at  Keweenaw  Point,  29. 

in  Alaska-Treadwell  mines,  145. 

in  Combination  Mine,  104. 

in  Trimountain  Mine,  130. 

Dams: 

for  holding  back  waste,  171. 

for  holding  back  bad  ground,  186. 
Dead-ends,  65. 

Depth  of  mining,  open  cut,  208.     , 
Development: 

application  of,  29. 

advantages  of  vertical  shafts,  36,  41. 

advantages  of  inclined  shafts,  36,  41. 

advantages  of  tunnel,  40. 

advantage  of  drifts  and  slopes,  40. 

controlling  factors,  30. 

costs,  249. 

disadvantages  of  vertical  shafts,  36, 
41. 

disadvantages  of  inclined  shafts,  37. 

disadvantages  of  drifts  and  slopes,  40. 

establishing  ore  reserves,  29. 

influence  of  faults,  32. 

influence  of  shape  of  deposit,  32. 

influence  of  dip,  32. 

in  Alaska-Treadwell  mine?,  144,  255. 

in  Baltic  and  Trimountain  mines,  129. 

in  Broken  Hill  mines,  158,  162. 

in  Combination  Mine,  106. 

in  Coeur  d'Alene  mines,  108,  115. 

in  diamond  mines  of  S.  Africa,  195, 

in  Gold  Prince  Mine,  Colo.,  140. 


INDEX 


271 


Development: 

in  Homestake  mines,  167. 

in  Lake  Superior  iron  mines,  top-slice 
method,  177,  181. 

in  Lake   Superior  iron  mines,   sub- 
drift  method,  181. 

in  Mercur  mines,  134. 

in  Miami  Mine,  190,  191. 

in  milling  method,  225. 

in  Queen  Mine,  52. 

in  steam-shovel  mining,  218. 

in  St.  Lawrence  Mine,  Butte,  Mont., 
123. 

in  Susquehanna  Mine,  Minn.,  186. 

in  Tonopah,  Nevada,  100. 

in  Zaruma  Mine,  Ecuador,  119. 

limits  of,  31. 

number  of  levels,  47. 

of  veins,  42,  44. 

of  massive  deposits,  43. 

references,  48. 

relation  to  output,  43,  46. 

systems,  47. 

tramming  limits,  46. 

use  of  drifts,  38,  40. 

use  of  inclines,  39,  97. 

use  of  cross-cuts,  42. 

use  of  slopes,  38,  39,  97. 

use  of  tunnels,  38. 

use  of  turned-vertical  shafts,  38. 

vertical  and  inclined  shafts,  33. 

within  deposit,  41. 
Diamond,  bearing  formations,  195. 
Diamond  mines  of  S.  Africa,  195. 

pipes  and  ducts,  195. 
Disposal  of  waste: 

in  open  cut  work,  217. 
Docks: 

in  open  cut,  hand  work,  210. 

in  open-stopes,  79. 
Dome  of  equilibrium,  21. 

arching  of  roof,  21. 

in  underground  milling  method,  224. 

when  used,  225. 
Drainage: 

in  strip-pits,  217. 
Drifts: 

blind,  145. 

in  diamond  mines,  199. 

in  Alaska-Treadwell  mines,  145. 

in  caving  pillars,  35. 

in  development,  38. 

in  diamond  mines  of  S.  Africa,  199. 

in  Lake  Superior  iron  mines,  181,  231. 

in  stopes,  147. 

sub,  145. 

Drill-shift  in  stoping,  262. 
Dry-walls  in  copper  mines,  128. 


Ely,  Nevada,  steam-shovel  work,  218. 
Exploration,  28. 

Filling: 

advantages,  5,  19. 

applications,  3,  19. 

back-filling,  122,  125. 

in  Homestake  mines,  166,  167,  170. 

distribution  of,  125. 

disadvantages  of  use,  4,  24. 

drawing  from  stope  to  stope,  117. 

in  Combination  Mine,  106. 

in  Hecla  Mine,  108. 

in  St.  Lawrence  Mine,  125. 

in  stopes,  103. 

in  Tonopah  mines,  103. 

references  to,  204. 

rock,  3. 

saving  in  cost,  67. 

source  of,  20,  130. 

tendency  to  become  quick,  24. 

use,  19. 

waste,  103,  117,  120,  130. 
Flooring,  1 88. 
Floors: 

boards  in  Susquehanna  Mine,  188. 

in  Broken  Hill  mines,  161. 

in  Homestake  Mine,  171. 

in  Rossland,  B.  C.,  mines,  52. 

sill,  13- 

stope,  79. 

stope  in  Homestake  mines,  147. 

stull,  100. 
Floor-boards  used  in  St.  Lawrence  Mine, 

126. 

Franklin  Mine,  128. 
Fracture  prismoid,  21. 

Galleries  in  diamond  mines,  S.  Africa, 

iQS- 
Glory-holes: 

how  name  was  derived,  209. 

in  milling  method,  228. 

underground  method,  224. 
Go-devil: 

in  gravity  planes,  80. 

in  stopes,  80. 

Golden  Gate  Mine,  Utah,  133. 
Gold  Prince  Mine,  Colo.,  140. 
Granby  mines,  British  Columbia: 

steam-shovel  work,  218. 
Gravity  plane  in  stopes,  80. 
Grizzly  in  glory-hole  mining,  229. 

Hand  mining: 

advantages  of,  214. 
disadvantages  of,  215. 
open  cut  work,  210. 


272 


INDEX 


Handling: 

back-filling  in  St.  Lawrence  Mine,  123. 

by  Chinaman  chute,  89. 

by  go-devil,  80. 

by  gravity  plane,  80. 

conveyors  in,  80. 

cost  of,  246. 

drawing-off-levels,  191. 

economic  limit,  78,  80. 

chute-raises,  191. 

in  closed  stopes,  78,  82. 

in  milling  method,  228. 

in  open  stopes,  78,  79,  169. 

methods  of,  78. 

on  docks,  79. 

ore  in  Bunker  Hill-Sullivan   mines, 

us- 

ore  in  cars,  82,  98. 

ore  in  Combination  Mine,  106. 

ore  in  Homestake  Mine,  169. 

ore  in  Lake  Superior  iron  mines,  185. 

ore  in  open  cuts,  handwork,  210. 

ore  in  stopes,  79,  82. 

raking,  79. 

references  to,  92. 

shoveling,  79,  170,  172,  202. 

the  monorail,  80. 

timber  in  Hecla  Mine,  113. 

timber  in  Lake  Superior  iron  mines, 
80. 

use  of  steel  metal  chutes,  44,  79,  80. 

waste  in  Bunker  Hill  mines,  115. 

waste  in  Homestake  Mine,  169. 

waste  in  St.  Lawrence  Mine,  125. 

Zaruma,  Ecuador,  119. 
Haulage- way : 

in  milling  method,  225. 
Head  boards  in  Hecla  Mine,  no. 
Hecla  Mine,  Coeur  d'Alene  district,  108. 
Heel  of  stope,  57. 
Hitch  in  placing  stulls,  9. 
Holes  in  drilling: 

dry,  69. 

wet,  69. 
Homestake  mines,  South  Dakota: 

advantages  of  methods  employed,  176. 

cost  of  support  in,  266,  267. 

depth  of  open  cuts,  208. 

description  of,  165. 

disadvantages  of  methods  employed, 
176. 

milling  method,  208. 

recent  method  of  mining,  65. 

stopes  in,  21. 

Inclines,  39. 
Iron  Mt.  Mine,  Mo. : 
depth  of  open  cuts,  208. 


Joplin  district,  258. 

Keweenaw  Point,  Mich.,  3,  251. 
temperatures  in  mines,  240. 

Labor: 

conditions  affecting,  237. 

costs,  240,  241,  243. 
Lagging: 

in  Hecla  Mine,  no. 

in  Homestake  mines,  169. 

in  Lake  Superior  iron  mines,  80. 

in  Queen  Mine,  154. 

use  of,  n. 

Lake  Superior  iron  mines,  80. 
Levels: 

dra  wing-off,  191. 

distance  apart  in  iron  mines,  97. 

distance  apart  in  Tonopah  mines,  100. 

distance  apart  in  diamond  mines  of 
S.  Africa,  96. 

in  Alaska-Treadwell  mines,  144. 

in  Baltic  Mine,  128. 

in  Broken  Hill  mines,  158. 

in  Combination  Mine,  104. 

in  diamond  mines,  199. 

in  Hecla  Mine,  108. 

in  Homestake  Mine,  166. 

in  Lake  Superior  iron  mines,  177. 

in  Zaruma  Mine,  119. 

intermediate,  in  diamond  mines,  196. 

protection  of,  84. 
Light,  cost  of,  245. 
Longwall  stoping,  66,  141. 

application  of,  66. 
Loss  of  ore: 

in  Combination  Mine,  107. 

in  diamond  mines,  S.  Africa,  202. 

in  Gold  Prince  Mine,  42. 

in  Homestake  mines,  174. 

Man- way: 

cribbed,  121. 

in  Broken  Hill  mines,  161. 

in  Bunker  Hill-Sullivan  Mine,  115. 

in  Lake  Superior  iron  mines,  177. 

in  St.  Lawrence  Mine,  123. 
Massive  deposits: 

development  of,  43. 

stoping  in,  60. 
Mat  of  timber: 

in  Homestake  Mine,  71. 

in  Lake  Superior  iron  mines,  80. 

in  Susquehanna  Mine,  88. 
Mercur  Mine,  133. 
Methods  of  Mining,  see  Mining. 
Milling: 

advantages  of,  232,  235. 


INDEX 


273 


Milling: 

disadvantages  of,  233. 

glory-holes,  209,  228,  230. 

in  iron  mines,  224,  225. 

method  in  ore  mining,  224,  225,  232. 

number  of  pits,  227. 

ores  best  suited  to  method,  228. 

pits,  227. 

underground,  225. 
Mill-holes: 

in  glory-hole  mining,  229. 

in  Trimountain  Mine,  129. 
Mines: 

Alaska-Treadwell,  142,  232. 

Atlantic,  128. 

Baltic,  128. 

Bingham  Canyon,  218,  232. 

Birmingham,  Ala.,  96. 

Broken  Hill,  Australia,  156. 

Bunker  Hill-Sullivan,  114. 

Central,  Mo.,  240. 

Cceur  d'Alene,  Idaho,  88,  114. 

Combination,  Goldfield,  Nev.,  104. 

Comstock  Lode,  232. 

Cripple  Creek,  254. 

Diamond,  S.  Africa,  195. 

Franklin,  128. 

Golden  Gate,  133. 

Gold  Prince,  Colo.,  140. 

Granby,  British  Columbia,  218,  232. 

Hecla,  Cceur  d'Alene  district,  108. 

Homestake,  S.  Dakota,  165. 

Iron  Mt.,  Mo.,  208. 

Keweenaw  Point,  Mich.,  3,  128,  251. 

Lake  Superior  iron,  152,  176, 177, 181. 

Mercur,  133. 

Miami  Mine,  189. 

North  Star,  80. 

Queen,  Negaunee,  152. 

Quincy,  128. 

St.  Lawrence,  Butte,  Mont.,  122. 

Susquehanna,  Minn.,  186. 

Tonopah,  Nev.,  100. 

Trimountain,  128. 

War  Eagle  Mine,  258. 

Zaruma,  S.  America,  119. 
Mining : 

advantages  of   stull  method,   Tono- 
pah Mine,  193. 

back-filling,  St.  Lawrence  Mine,  122. 

by  filling,  19. 

by  hand,  in  open  cuts,  210. 

by  scrapers,  215. 

by  steam  shovels,  218. 

caving: 

in  diamond  mines,  199. 
in  Mercur  mines,  135. 
in  Miami  Mine,  189,  194. 


Mining: 

caving:  in  Michigan  iron  mines,  176. 

methods,  5,  21. 
costs,  247,  248,  249. 
disadvantages  of  stull  method,  Tono- 
pah Mine,  103. 
filling,  19. 

in   copper   mines,   Lake   Superior, 

128. 

Glory-hole  methods,  209,  228,  230. 
Gold  Prince  Mine,  140. 
in  Alaska-Treadwell  mines,  144. 
in  bedded  deposits  with  props,  96. 
inclined  floors,  119. 
iron  mines,  Birmingham,  Ala.,  96. 
methods,  95. 

milling  method,  224,  225,  232. 
open  cut  mining,  208. 
over-hand    stoping    in    Combination 

Mine,  104. 

rill  stoping  in  Zaruma  Mine,  119. 
room-and-pillar,  96. 
square-set  method,  Rossland,  B.  C., 

51- 

sub-drift  method  of,  181. 
in  diamond  mines,  199. 
in  Lake  Superior  iron  mines,  181, 

231. 

top-slice  method,  177. 
Mixing  of  ore  and  waste,  25. 
Mud    rushes    .in    diamond    mines,    S. 
Africa,  202. 

Open  cut: 

advantages  of,  214,  234. 

Alaska-Treadwell  mines,  Alaska,  208. 

by  hand,  210. 

by  steam  shovels,  218. 

depth  of,  208. 

diamond  mines,  S.  Africa,  208. 

disadvantages  of,  215,  234. 

Glory-hole  mining,  209,  230. 

Homestake  mines,  S.  D.,  208. 

in  diamond  mines,  195. 

Iron  Mountain  Mine,  Mo.,  208. 

keeping  separate,  ore  and  waste,  229. 

mining  in  general,  208. 

references  to,  236. 

Rio  Tinto  mines,  Spain,  208. 
Open-stope  method  of  mining,  78,  79, 
169. 

in  Broken  Hill  mines,  158. 
Ore  pockets,  stopes  in  Homestake  mines, 

174. 
Ore  reserve,  19,  28,  29,  42,  55,  69. 

advantages  of,  29,  69. 

as  filling,  19. 

in  Gold  Prince  Mine,  141. 


274 


INDEX 


Ore  reserve,  in  stoping,  69. 
Ore,  hard  and  soft  iron,  97. 

suited  to  steam-shovel  work,  221. 

output  of  mines,  46. 
Overburden : 

maximum   and   minimum   thickness, 
215,  219. 

removal  of,  by  steam  shovel,  218. 
Overhand  stoping: 

advantages  of,  68. 

application,  53,  58 

conditions  affecting  working,  54. 

disadvantages  of,  68. 

in  Bunker  Hill-Sullivan  Mine,  114. 

in  Combination  Mine,  104. 

in  Hecla  Mine,   Cceur  d'Alene  dis- 
trict, 108. 

in  milling  method,  227. 

in  Tonopah  Mine,  101. 

in  Zaruma  Mine,  S.  America,  120. 

method,  53. 

method  of  attack,  55. 

Pack-walls : 

Trimountain  Mine,  128. 
Pent  ices  in  Alaska-Tread  well  mines,  47. 
Pickers  in  Trimountain  Mine,  130. 
Pillar-and-stope  method  of  mining,  62. 
Pillar-drawing : 

in  Broken  Hill  mines,  164. 

in  diamond  mines,  S.  Africa,  199. 

in  Homestake  mines,  171,  174. 

in  iron  mines,  98. 

in  Lake  Superior  iron  mines,  183. 

in  Mercur  mines,  135. 

in  Miami  Mine,  190,  191. 

in  milling  method,  225. 

in  Queen  Mine,  52. 

in  sub-drift  system,  183. 

in  Susquehanna  Mine,  186. 
Pillars: 

advantages  of  use,  22, 

arch,  7,  164. 

dead-ends,  65. 

disadvantages,  22. 

distance  between,  8. 

drawing,  98. 

failure  of,  7. 

forms  of,  7. 

in  Ala  ska-Tread  well  mines,  144. 

in  Gold  Prince  Mine,  140. 

in  Lake  Superior  iron  mines,  54. 

irregularity  in  forming  and  placing,  7. 

lacing  in  Homestake  mines,  74. 

objection  to  use  of,  6. 

pentices  in  Alaska-Treadwell  mines, 
147. 

position  of.  7,  84. 


Pillars: 

robbing  of,  97,  155,  164,  171. 

drawing,  97. 

shaft,  7. 

sheet,    in    Alaska-Treadwell    mines, 
147. 

size  of,  7,  97,  140. 

stump  in  Gold  Prince  Mine   142. 

wall,  8. 

weakening  by  undercutting  in  Home- 
stake  mines,  72. 

Pipes  or  ducts,  in  diamond  mines,  95. 
Props: 

advantages  of,  22. 

application  of,  n. 

disadvantages  of,  22. 

distance  apart  in  iron  mines,  98. 

in  mining  iron  ore,  98. 

in  St.  Lawrence  Mine,  Butte,  Mont., 
125. 

methods  of  setting,  8. 

size  in  iron  mines,  98. 
Posts: 

advantages  of,  22. 

in  the  Mercur  Mine,  135. 

in  Zaruma  Mine,  121. 

methods  of  setting,  8. 

with  stull-sets,  108. 

square-sets,  14. 
Prospecting,  28. 

Quarry,  open  cut  work,  213. 
Queen  Mine,  Negaunee,  152. 
Quincy,  Mine,  128. 

Raises : 

chute,  191. 
in  Alaska-Treadwell  Mine,  144. 

cost  of,  250. 

for  ventilation,  145. 

in  Alaska-Treadwell  mines,  145. 

in  Glory -hole  mining,  227. 

in  Homestake  mines,  169. 

in  Lake  Superior  iron  mines,  181. 

in  milling  method,  227. 

in  stoping,  53. 

pillar,  191. 

use  of,  in  stoping,  53,  125,  181. 
Raking  ore  in  stopes,  79. 
Resuing,  51,  66,  71. 

advantage  of,  71. 

application  of,  66. 
Rill  stoping: 

advantages  of,  121. 

designation,  121. 

disadvantages  of,  122. 

in  Broken  Hill  mines,  161. 
»  in  diamond  mines,  S.  Africa,  199. 


INDEX 


275 


Rill  stoping: 

in  Trimountain  and  Baltic  mines,  132. 

in  Zaruma  mines,  119. 
Rock  walls: 

in  copper  mines,  128. 
Roof  of  galleries  in  diamond  mines  of 

S.  Africa,  199. 
Room  and  pillar  working: 

in  Alaska-Treadwell  Mine,  142. 

in  Homestake  Mine,  165. 

in  iron  mines,  Birmingham,  Ala.,  97. 

in  Lake  Superior  iron  mines,  52. 

Scraper: 

advantages  of,  217. 

disadvantages  of,  218. 

drag  in  open  cut  working,  215. 

in  open  cut  working,  215. 

shafts,  vertical  and  inclined,  33,  97. 
cost  of,  250. 

use  in  development,  33. 

turned- vertical,  38. 
Shaft  pillars,  7. 

in  iron  mines,  97. 
Sheet-pillars: 

in  Alaska-Treadwell  mines,  147. 
Shoveling: 

in  Homestake  mines,  170,  172. 

in  Lake  Superior  iron  mines,  183. 

in  open  cut  work,  hand  mining,  210. 

in  stopes,  79,  202. 

in  Susquehanna  iron  mine,  188. 
Shovelers: 

in  Homestake  mines,  170. 
Shrinkage  stoping: 

description  of,  140,  189. 

in  Alaska-Treadwell  mines,  144. 

in  Gold  Prince  Mine,  140. 

in  Homestake  Mine,  67,  172. 
Side  stoping: 

application,  65. 

objection  to  use,  65. 
Side-swiping  in  Mercur  Mine,  133. 
Slices : 

inclined,  in  Broken  Hill  mines,  161. 

in  Zaruma  Mine,  119. 
Slopes,  38,  39,  97. 
Sorting: 

in  Hecla  Mine,  113. 

in  resuing,  67. 

in  Trimountain  Mine,  129. 

in  Zaruma  Mine,  122. 

in  Trimountain  Mine,  129. 

of  waste  in  stoping,  125. 
Spread  of  costs,  247. 
Square-sets: 

advantages  of,  213. 

application  of,  13,  17. 


Square-sets : 

cause  of  failure,  117. 

cause  of,  in  Homestake  mines,  66. 

disadvantages  of  use,  23. 

economy  of  use,  265. 

framing  of,  15. 

in  British  Columbia  mines,  150. 

in  Broken  Hill  mines,  156. 

in  Comstock  mines,  4. 

in  Cceur  d'Alene  mines,  114,  117. 

in  Homestake  mines,  167,  172. 

in  Queen  Mine,  Negaunee,  Mich.,  54. 

in  Rossland,  B.  C.,  mines,  152. 

in  St.  Lawrence  Mine,  123. 

in  Tonopah  mines,  103. 

method  of  placing,  13. 

parts  of,  14. 

references  to,  202. 

size  of,  in  Bunker  Hill-Sullivan  mines, 

US- 
size  and  length  of  posts,  15. 
size  of,  in  Rossland,  B.  C.,  mines,  152. 
use  of  parts  of  sets,  15. 
used  with  stulls,  12. 
when  applicable,  13,  95. 
with  round  timber,  in  Rossland  mines, 

151- 
Steam-shovel  work: 

advantages  of,  223. 

broken-boom,  223. 

description  of,  219. 

development  of,  219. 

disadvantages  of,  223. 

in  milling  method,  228. 

in  open  cut  work,  218,  228. 

in  phosphate  mining,  222. 

loading  stock  piles,  222. 

methods  of,  219,  222. 

operation,  221. 

references  to,  235. 

when  applicable,  223. 
Stock  piles,  29,  222. 

St.  Lawrence  Mine,  Butte,  Mont.,  122. 
Stoping: 

application,  52. 

back,  57,  108,  152. 

beginning   of   underhand   and   over- 
hand, 55,  58. 

breast,  51,  64,  98,  161. 

classification  of  methods,  52. 

combined,  51,  63,  71. 

conditions  affecting  choice  of  method, 
52. 

Cornish  system,  58. 

cost  of,  250. 

cutting-out,  55,  57,  104,  130. 

drift,  57,  145. 

in  Bunker  Hill-Sullivan  mines,  115. 


276 


INDEX 


Stoping: 

in  Broken  Hill  mines,  64. 

in  Gold  Prince  Mine,  Colo.,  140. 

influence  of  character  of  walls  and  ore, 

54- 

influence  of  dip,  52. 
cost  of,  250,  251,  252,  253,  256,  257, 

259,  260. 

influence  of  handling  ore  in  stopes,  53. 
in  Queen  Mine,  Mich.,  52. 
longwall,  51,  66,  72. 
methods  of,  51. 

overhand,  51,  53,  67,  140,  199,  227. 
powder  used,  240. 
practice  in  the  United  States,  53. 
raise,  55. 
rate  of,  240,  251. 
references  to,  73. 
resuing,  51,  66,  71. 
resume  of,  67. 
rill,  in  Broken  Hill  mines,  119,  121. 

in  diamond  mines,   South  Africa, 
199. 

in  Trimountain  and  Baltic  mines, 
128. 

in  Zaruma  mines,  119. 
shrinkage,  55,  140,  189. 
side,  51,  65,  72,  135. 

in  Mercur  mines,  133. 
underhand,  51,  58,  96,  227. 
where  ore  is  of  uniform  value,  "54. 
Stopes: 

back,  57,  161,  169. 
back  of,  113. 

circular,   in  milling  method,   under- 
ground, 227. 
closed,  78,  82. 
collapse  of  large,  6. 
drift,  57. 
floors  in  Alaska-Treadwell  mines,  147. 

in  Queen  Mine,  Mich.,  154. 

in  Miami  Mine,  191. 
handling  in,  78. 
heel  of,  57. 
height  in  Broken  Hill  mines,  161. 

in  Homestake  mines,  166,  172. 
height  of,  149,  230. 
in  iron,  Birmingham,  Ala.,  96. 
.      in  Broken  Hill  mines,  161. 

in  diamond  mines,  South  Africa,  199. 

in  Homestake  mines,  166,  172. 

in  iron  mines,  97. 

in  Miami  Mine,  189. 

in  St.  Lawrence  Mine,  123. 

in  Tonopah  mines,  100. 

open,  79. 

opening  of,  55,  167,  199. 

opening  of,  in  diamond  mines,  199. 


Stopes: 

opening  of  underhand,  58. 

ore  pockets  in  Homestake  mines,  174. 

raise,  55,  191. 

stope  faces,  57. 

toe  of,  57. 

width  of,  in  Homestake  mines,  67, 

.  T7?- 
Strip-pits: 

drainage  in,  217. 

increase  of  size  by  wheel  scrapers,  215, 
217. 

in  working  coal,  209,  216. 

size  of,  215. 
Stripping: 

as  applied  to  removal  of  pillars,  183. 

in  open  cut  mining,  209. 

in  stoping,  183,  185. 

pits,  209. 
Stull:  < 

application  of,  u. 

floors,  100,  101. 

headings  in  Tonopah  Mine,  101. 
in  Hecla  Mine,  no. 

in  Tonopah  Mine,  101. 

level,  104. 

rooms,  230. 

waste,  ii. 
Stull-set  mining: 

advantages  of,  113. 

disadvantages  of,  114. 

in  Hecla  Mine,  108. 
Stulls: 

advantages  of,  23. 

angle  of  underlie,  9. 

battery  of,  n. 

disadvantages  of,  9. 

in  Coeur  d'Alene  mines,  108. 

in  Combination  Mine,  106. 

in  Michigan  mines,  3. 

in  St.  Lawrence  Mine,  122. 

in  Tonopah  mines,  123. 

lagged,  u. 

method  of  placing,  9. 

waste,  ii. 

when  placed,  ii. 

winged,  85. 

with  props,  ir. 

with  square-sets,  ii. 
Stull-floors,  100,  101. 
Stull-set.  Hecla  Mine,  108. 
Sub-drifts: 

advantages  of,  189. 

blind,  in  Alaska-Treadwell  mines,  145. 

disadvantages  of,  189. 

distance  apart  in  diamond  mines,  195. 

in  Alaska-Treadwell  mines,  145. 

in  diamond  mines,  199. 


INDEX 


277 


Sub-drifts: 

in  Lake  Superior  iron  mines,  181,  231. 

in  Mercur  mines,  133. 

method  of  mining,  81. 
advantages  of,  189. 
disadvantages  of,  189. 
in  Susquehanna  Mine,  Minn.,  186. 

sub-levels,  191. 
Support: 

by  filling,  19. 

by  stull-sets,  108. 

cost  of  238,  246. 

cost  of  square-sets,  246. 

indirect  methods,  6,  21. 

methods  of,  5,  6. 

ore  in  stopes,  19. 

pillars  of  ore  or  waste,  6. 
Supplies  in  stoping,  244. 
Susquehanna  Mine,  Minn.,  186. 

Temperatures  in  mining,  240. 
Terraces: 

in  diamond  mines  of  S.  Africa,  198. 

in  iron  mines,  222. 

in  open  cut  work,  212. 

in  steam-shovel  work,  221. 
Test  pits,  proving  deposits,  219, 
Tight  corner  in  stoping,  63. 
Timber: 

A- form  in  Queen  Mine,  154.. 

in  stull-rooms,  230. 

cantilever  supports,  161. 

corduroy,  3. 

cribs,  6,  13,  23,  161. 

economy  in  use  of,  Homestake  Mine, 
166. 

for  mine  use,  8. 

handling  of,  186. 

in  diamond  mines,  199. 

in  Homestake  mines,  171. 

in  Lake  Superior  iron  mines,  180,  181, 
183. 

kinds  of,  8. 

lacing  in  Homestake  mines,  174. 

props,  6. 

scarcity  of,  8. 

size  of: 

in  Rossland,  B.  C.,  mines,  152. 
in  Susquehanna  Mine,  188. 
in  Tonopah  Mine,  101. 

slides  in  Hecla  Mine,  in. 

square-sets,  13,  103,  171. 


Timber: 

use  of  broken,  125. 

use  of,  with  caving,  5. 

wall-pieces  in  Trimountain  Mine,  129. 
Toe  of  stope,  57. 
Tonopah  Mine,  Nev.,  101. 
Top-slice  method  of  mining,  177. 

advantages  of,  180. 

disadvantages  of,  181. 
Trammers,  130. 
Tramming  limits,  46. 
Trimountain  Mine,  128. 
Tunnels  in  development,  38. 

Underhand  stoping: 
advantages  of,  69. 
application  of,  58,  59,  60,  96. 
disadvantages  of,  69. 
in  milling  method,  227. 
in  Combination  Mine,  106. 

Ventilation: 

in  Combination  Mine,  107. 
in  diamond  mines,  S.  Africa,  202. 
in  Tonopah  Mine,  103. 
raises  for,  in  Alaska-Treadwell  mines, 
45- 

Wages,  189. 

Wall-pieces  in  Baltic  and  Trimountain 

mines,  128. 
Wall  pillars,  7. 
Waste: 

as  filling,  19,  113,  126,  130,  164,  169. 

advantages,  19. 

source  of,  20,  130. 
Waste  bank,  open  cut  work,  217. 
War  Eagle  Mine,  258. 
Wheelbarrows: 

use  in  stopes,  72. 

use  in  top-slice  method,  iron  mines, 

178. 

Winged  stulls,  see  Stulls,  85. 
Winzes: 

cost  of,  250. 

in  Coeur  d'Alene  mines,  115. 

in  St.  Lawrence  mines,  Butte,  123. 
Woods,  see  Timber,  8. 

Yates,  B.  C.,  265. 

Zaruma  Mine,  South  America,  119. 


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